Piezoelectric element, ink jet head, angular velocity sensor, method for manufacturing the same, and ink jet recording apparatus

ABSTRACT

A piezoelectric element includes a first electrode layer  14  provided on a substrate  11  and made of a noble metal to which at least one additive selected from the group consisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added, an orientation control layer  15  provided on the first electrode layer  14  and made of a cubic or tetragonal perovskite oxide that is preferentially oriented along a (100) or (001) plane, and a piezoelectric layer  16  provided on the orientation control layer  15  and made of a rhombohedral or tetragonal perovskite oxide that is preferentially oriented along a (001) plane.

BACKGROUND OF THE INVENTION

The present invention relates to a piezoelectric element having anelectro-mechanical conversion function, an ink jet head using thepiezoelectric element, an angular sensor, a method for manufacturing thesame, and an ink jet recording apparatus including the ink jet head asprinting means.

Generally, a piezoelectric material is a material capable of convertinga mechanical energy to an electrical energy and vice versa. A typicalexample of a piezoelectric material is lead zirconate titanate having aperovskite crystalline structure (Pb(Zr,Ti)O₃) (hereinafter referred toas “PZT”). In PZT, the greatest piezoelectric displacement is obtainedin the <001> direction (the c axis direction) in the case of atetragonal system, and in the <111> direction in the case of arhombohedral system. However, many of the piezoelectric materials arepolycrystals made up of a collection of crystal grains, and thecrystallographic axes of the crystal grains are oriented randomly.Therefore, the spontaneous polarizations Ps are also arranged randomly.

Along with the recent downsizing of electronic appliances, there is astrong demand for reducing the size of piezoelectric elements using apiezoelectric material. In order to meet the demand, more piezoelectricelements are used in the form of thin films whose volumes can besignificantly reduced from those of sinters, which have conventionallybeen used in various applications, and active researches anddevelopments have been made for reducing the thickness of thin-filmpiezoelectric elements. For example, in the case of tetragonal PZT, thespontaneous polarization Ps is oriented in the c axis direction.Therefore, in order to realize superior piezoelectric characteristicseven with a reduced thickness, the c axes of crystal grains forming aPZT thin film need to be aligned vertical to the substrate plane. Inorder to realize such an alignment, a sputtering method has been used inthe prior art. Specifically, on a single crystal substrate made ofmagnesium oxide (MgO) having an NaCl-type crystalline structure, whichhas been cut out so that the surface thereof is along the crystalorientation of the (100) plane, a (100)-oriented Pt electrode thin filmis formed as a lower electrode on the substrate, and a PZT thin filmwhose c axis is oriented vertical to the surface of the Pt electrode isformed on the Pt electrode at a temperature of 600 to 700° C. (see, forexample, Journal of Applied Physics vol. 65 No. 4 (published on 15 Feb.1989 from the American Physical Society) pp. 1666-1670, and JapaneseLaid-Open Patent Publication No. 10-209517). In such a case, if apiezoelectric element layer having a thickness of 0.1 μm and made ofPbTiO₃ or (Pb,La)TiO₃, free of Zr, is formed as a base layer for a PZTthin film on the (100)-oriented Pt electrode before the formation of aPZT thin film, and then a PZT thin film having a thickness of 2.5 μm isformed on the piezoelectric element layer by a sputtering method, it isless likely that a layer of a low crystallinity made of a Zr oxide isformed early in the formation of the PZT thin film, thereby obtaining aPZT thin film having a higher crystallinity. Specifically, a PZT thinfilm whose degree of (001) orientation (“α(001)”) is about 100% isobtained.

Herein, α(001) is defined as follows:

-   -   α(001)=I(001)ΣI(hkl).

ΣI(hkl) is the sum of diffraction peak intensities from various crystalplanes of PZT having a perovskite crystalline structure for a Cu-Kα 2θrange of 10° to 70° in an X-ray diffraction method. Note that the (002)plane and the (200) plane are not included in ΣI(hkl) as they areequivalent to the (001) plane and (100) plane.

However, this method uses an MgO single crystal substrate as a basesubstrate, thereby increasing the cost of a piezoelectric element, andthus the cost of an ink jet head using the piezoelectric element.Moreover, another drawback is that the variety of the substrate materialis limited to the MgO single crystal.

In view of this, various methods have been developed for forming a(001)- or (100)-oriented film of a perovskite piezoelectric materialsuch as PZT on an inexpensive substrate such as a silicon substrate. Forexample, Japanese Laid-Open Patent Publication No. 6-116095 disclosesthat a PZT film that is preferentially oriented along the (100) planecan be produced by applying a precursor solution of PZT orlanthanum-containing PZT on a (111)-oriented Pt electrode, performing athermal decomposition process at 450 to 550° C. before the precursorsolution is crystallized and then heating and crystallizing theprecursor solution at 550 to 800° C. (a sol-gel method).

Moreover, Japanese Laid-Open Patent Publication No. 2001-88294 disclosesthat by forming a very thin titanium layer on an iridium lowerelectrode, it is possible to control the crystal orientation of a PZTfilm to be formed thereon. This manufacturing method includes: forming abase layer whose main component is zirconium oxide on a substrate madeof silicon, or the like; forming a lower electrode containing iridium onthe base layer; depositing a very thin titanium layer on the lowerelectrode; forming an amorphous piezoelectric precursor thin filmcontaining metal element and oxygen element, which forms a ferroelectrichaving piezoelectric characteristics, on the titanium layer; and heatingand crystallizing the amorphous thin film at a high temperature (asol-gel method), thereby turning the amorphous thin film into aperovskite piezoelectric thin film. With this manufacturing method, thecrystal orientation of the piezoelectric thin film such as PZT can becontrolled by the thickness of the titanium layer, and a (100)-orientedfilm is obtained when the thickness of the titanium layer is set to be 2to 10 nm.

Furthermore, Japanese Laid-Open Patent Publication No. 11-191646discloses that where a piezoelectric thin film is formed by using asol-gel method, a (100)-oriented PZT film can be obtained by forming atitanium layer having a thickness of 4 to 6 nm on a (111)-oriented Ptelectrode and using titanium oxide, which is formed through oxidizationof titanium in the titanium layer, as a nucleus.

However, while the methods described above are desirable methods that donot use an expensive MgO single-crystal substrate, it is difficult toobtain a well-oriented film having a desirable crystallinity in the filmformation process, as in the case of forming a piezoelectric thin filmon an MgO single-crystal substrate, because the piezoelectric thin filmis formed by a sol-gel method. In view of this, an amorphouspiezoelectric thin film is first formed, and then the layered structureincluding the substrate and the piezoelectric thin film is subjected toa heat treatment, so that the crystallographic axes are preferentiallyoriented in a desirable direction.

Moreover, when piezoelectric elements are mass-produced with a sol-gelmethod, the amorphous piezoelectric precursor thin film is likely to becracked due to changes in the volume during the degreasing step ofremoving organic substances. Furthermore, in the step of heating andcrystallizing the amorphous piezoelectric precursor thin film at a hightemperature, the film is likely to be cracked or peeled off from thelower electrode due to crystal changes.

As a solution to these problems with a sol-gel method, JapaneseLaid-Open Patent Publication Nos. 2000-252544 and 10-81016 disclose thatit is effective to add titanium or titanium oxide in the lowerelectrode. Particularly, Japanese Laid-Open Patent Publication No.10-81016 shows that a (100)-oriented PZT film can be obtained even witha sputtering method. Note however that a perovskite PZT film is notobtained directly on the lower electrode. First, a PZT film having anamorphous or pyrochlore crystalline structure is formed at a lowtemperature of 200° C. or less, which is then crystallized through aheat treatment at a high temperature of 500 to 700° C. in an oxygenatmosphere. Therefore, as with a sol-gel method, the film is likely tobe cracked or peeled off from the lower electrode due to crystal changesin the step of heating and crystallizing the film at a high temperature.Moreover, the degree of (001) orientation or the degree of (100)orientation of the PZT film formed by a sol-gel method or a sputteringmethod as described above is 85% or less with either method.

Furthermore, with a sol-gel method, the maximum thickness of the PZTfilm to be formed in a single iteration of the step (including theapplication of the precursor solution and the following heat treatment)is about 100 nm at maximum. Therefore, in order to obtain a thickness of1 μm or more, which is required for a piezoelectric element, it isnecessary to repeat this step ten times or more, whereby the productionyield may be reduced.

On the other hand, according to Japanese Laid-Open Patent PublicationNo. 2001-88294, supra, states that attempts were made to control theorientation of PZT on an Ir base electrode with a very thin titaniumlayer formed thereon by using a method other than a sol-gel method(including an MOD method) (in which an amorphous thin film is onceformed and then the thin film is turned into a crystalline thin filmthrough an aftertreatment such as a heat treatment), i.e., by using amethod in which a crystalline thin film is directly formed without thecrystallization step using a heat treatment, e.g., a sputtering method,a laser ablation method or a CVD method, and that a well-oriented filmwas not obtained with any method other than a sol-gel method. The reasonis stated to be as follows. The crystallization of the PZT film proceedsgradually from the lower electrode side to the upper electrode side witha sol-gel method, whereas with a CVD method or a sputtering method, thecrystallization of the PZT film proceeds randomly, resulting inirregular crystallization, and thus making the orientation controldifficult.

Moreover, when a titanium oxide film whose thickness is 12 nm or less isformed on a (111)-oriented Pt electrode layer, and a lead titanate filmor a PZT film having a perovskite crystalline structure is formeddirectly by a sputtering method, either film exhibits a (111)orientation property, and a (100)- or (001)-oriented film is notobtained (see Journal of Applied Physics vol. 83 No. 7 (published on 1Apr. 1998 from the American Physical Society) pp. 3835-3841).

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and has anobject to provide a reliable piezoelectric element with desirablepiezoelectric characteristics at low cost.

In order to achieve the object set forth above, the present inventionuses an electrode layer made of a noble metal to which at least oneadditive selected from the group consisting of Mg, Ca, Sr, Ba, Al andoxides thereof is added, and a piezoelectric layer made of arhombohedral or tetragonal perovskite oxide is formed on the electrodelayer so that the piezoelectric layer is preferentially oriented alongthe (001) plane.

Specifically, a piezoelectric element of the present invention includes:a first electrode layer; a piezoelectric layer provided on the firstelectrode layer; and a second electrode layer provided on thepiezoelectric layer, wherein: the first electrode layer is made of anoble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added; and thepiezoelectric layer is made of a rhombohedral or tetragonal perovskiteoxide that is preferentially oriented along a (001) plane.

With such a structure, if the first electrode layer is formed on asubstrate and the piezoelectric layer is formed on the first electrodelayer by a sputtering method, or the like, the piezoelectric layer islikely to be oriented along the (001) plane (since the (100) plane andthe (001) plane are the same in a rhombohedral system, the rhombohedral(100) orientation is included herein), even if the first electrode layeris oriented along the (111) plane. Specifically, the additive added tothe noble metal of the first electrode layer exists in a dotted patternon the surface of the first electrode layer. Since Mg, Ca, Sr, Ba(alkaline-earth metals) and Al, which are used herein as additives, areeasily oxidized, even if the additive is not used in the form of anoxide, the additive existing in a dotted pattern on the surface isturned into an oxide if oxygen is present when forming the piezoelectriclayer, etc. Since an oxide of Mg, Ca, Sr or Ba is an NaCl-type oxidehaving the same crystalline structure as that of an MgO substrate, thepiezoelectric layer is grown over the additive (oxide) using it as anucleus, whereby it is likely to be oriented along the (001) plane overthe additive. Moreover, for Al, there is only one kind of oxide, Al₂O₃,which is a stable oxide. Therefore, by optimizing the conditions forforming the piezoelectric layer, the piezoelectric layer is grown overAl (aluminum oxide) using it as a nucleus and is stably oriented alongthe (001) plane. Note that Al, whose oxide is stable, is advantageous inthat it makes easier to manage the process of manufacturingpiezoelectric elements, and it has a desirable environment resistance.

On the other hand, the first electrode layer is normally oriented alongthe (111) plane when a silicon substrate, or the like, is used.Therefore, a region of the piezoelectric layer above a portion of thesurface of the first electrode layer where the additive does not existmay be oriented in a direction other than along the (001) plane (e.g.,along the (111) plane) or may be amorphous. However, such a region thatis not oriented along the (001) plane extends only in the vicinity ofthe surface of the piezoelectric layer that is closer to the firstelectrode layer (i.e., within a distance of about 20 nm at maximum fromthe surface). Specifically, since a (001)-oriented portion grows moreeasily in an oxygen-containing deposition atmosphere, the (001)-orientedportion of the piezoelectric film formed over the additive grows at ahigher rate. Therefore, the (001)-oriented portion grows while graduallyexpanding in the lateral direction to form an inverted cone shape, andwhile suppressing the growth of crystal grains oriented along a planeother than the (001) plane along which the crystal growth rate is low(e.g., grains oriented along the (111) plane). Thus, as the crystalgrowth process proceeds, the cross-sectional area of the (001)-orientedregion taken along the plane perpendicular to the thickness directiongradually increases, while the region that is not oriented along the(001) plane gradually shrinks, in the direction away from the firstelectrode layer toward the other side (i.e., toward the second electrodelayer). When the thickness of the piezoelectric layer is about 20 nm,the (001)-oriented region extends substantially across the entiresurface. As a result, if the thickness of the piezoelectric layer is setto be 0.5 μm or more, it is possible to sufficiently obtain a degree of(001) orientation of 90% or more.

Therefore, even with a deposition method, other than a sol-gel method,in which a crystalline thin film is directly formed on an inexpensivesubstrate such as a silicon substrate without the crystallization stepusing a heat treatment (e.g., a sputtering method or a CVD method), itis possible to obtain a piezoelectric layer with a desirableorientation, whereby it is possible to suppress the deviation in thepiezoelectric characteristics of the piezoelectric element and toimprove the reliability thereof As the piezoelectric element is usedwhile applying an electric field in the direction vertical to thesurface of the piezoelectric layer thereof, the (001) orientation isadvantageous, particularly with a tetragonal perovskite PZT film,because the direction of the electric field is then parallel to the<001> polarization axis direction, thus resulting in an increasedpiezoelectric effect. Moreover, since the polarization rotation due tothe application of an electric field does not occur, it is possible tosuppress the deviation in the piezoelectric characteristics of thepiezoelectric element and to improve the reliability thereof On theother hand, with a rhombohedral perovskite PZT film, since thepolarization axis extends in the <111> direction, the (100) orientationresults in an angle of about 54° between the direction of the electricfield and the direction of the polarization axis. Nevertheless, byimproving the (100) orientation property, the polarization can keep aconstant angle with respect to the electric field application.Therefore, also in this case, the polarization rotation due to theelectric field application does not occur, whereby it is possible tosuppress the deviation in the piezoelectric characteristics of thepiezoelectric element and to improve the reliability thereof (forexample, in a non-oriented PZT film, the polarization axes are orientedin various directions, and application of an electric field urges thepolarization axes to be aligned parallel to the electric field, wherebythe piezoelectric characteristics may become voltage dependent and varysignificantly, or a sufficient reliability may not be maintained due toaging).

Moreover, a piezoelectric layer having a desirable orientation is easilyobtained without using an expensive MgO single-crystal substrate.Therefore, it is possible to reduce the manufacturing cost by using aninexpensive substrate, such as a glass substrate, a metal substrate, aceramic substrate or an Si substrate.

Furthermore, even if the thickness of the piezoelectric layer is 1 μm ormore, it is not necessary to repeat the same step a number of times, aswith a sol-gel method, and the piezoelectric layer can be formed easilyby a sputtering method, or the like. Thus, it is possible to suppress adecrease in the production yield.

In the piezoelectric element of the present invention, it is preferredthat an orientation control layer made of a cubic or tetragonalperovskite oxide that is preferentially oriented along a (100) or (001)plane is provided between the first electrode layer and thepiezoelectric layer.

In this way, by forming the orientation control layer on the firstelectrode layer by a sputtering method, or the like, the orientationcontrol layer is likely to be oriented along the (100) or (001) plane(the (100) plane and the (001) plane are the same in a cubic system), asis the piezoelectric layer of the piezoelectric element, even if thefirst electrode layer is oriented along the (111) plane, or the like. Byforming a piezoelectric layer having a similar crystalline structure tothat of the orientation control layer on the orientation control layer,the piezoelectric layer will be oriented along the (001) plane due tothe orientation control layer. With the provision of such an orientationcontrol layer, it is possible to use a piezoelectric material ofdesirable piezoelectric characteristics for the piezoelectric layerwhile using a material capable of further improving the crystallinity orthe orientation for the orientation control layer. As a result, it ispossible to easily obtain a piezoelectric layer with a high crystalorientation and a high stability. Note that in the orientation controllayer, a region that is not oriented along the (100) or (001) plane maybe present not only in the vicinity of the surface of the firstelectrode layer but also on the piezoelectric layer side. Even in such acase, if the thickness of the orientation control layer is 0.01 μm ormore, a (100)- or (001)-oriented region extends across a major portionof the surface of the orientation control layer that is closer to thepiezoelectric layer, with the degree of (001) orientation of thepiezoelectric layer being as high as 90% or more.

It is preferred that the orientation control layer is made of leadlanthanum zirconate titanate whose zirconium content is equal to orgreater than zero and less than or equal to 20 mol % and whose lanthanumcontent is greater than zero and less than or equal to 30 mol %.

By using such a lead lanthanum zirconate titanate material (PLZT;including the composition where the zirconium content is zero, i.e.,lead lanthanum titanate (PLT)) for the orientation control layer, theorientation control layer is even more likely to be oriented along the(100) or (001) plane, whereby it is possible to improve the orientationof the piezoelectric layer. In addition, by setting the zirconiumcontent to be less than or equal to 20 mol %, it is less likely that alayer of a low crystallinity made of a Zr oxide is formed early in thecrystal growth process. This, in combination with setting the lanthanumcontent to be less than or equal to 30 mol %, reliably suppresses adecrease in the crystallinity of the orientation control layer, therebyincreasing the breakdown voltage. Therefore, it is possible to reliablyimprove the crystallinity or the orientation of the piezoelectric layer,and to further improve the piezoelectric characteristics of thepiezoelectric element.

Moreover, the orientation control layer may be made of astrontium-containing perovskite oxide. In such a case, it is preferredthat the orientation control layer contains strontium titanate.

A strontium-containing perovskite oxide can be formed at lowertemperatures as compared with PZT, and the like, and it is more likely,with a strontium-containing perovskite oxide, that a thin film having adesirable orientation and a desirable crystallinity is obtained.Particularly, when strontium titanate is contained, it is possible toreliably improve the (100) or (001) orientation property and thecrystallinity of the orientation control layer, and thus the orientationof the piezoelectric layer.

It is preferred that a strontium titanate content of the orientationcontrol layer is equal to or greater than 5 mol % and less than or equalto 100 mol %.

If strontium titanate is contained in an amount of 5 mol % or more, theorientation and the crystallinity of the orientation control layer canbe improved reliably. In such a case, the orientation control layer maybe made only of strontium titanate (i.e., strontium titanate containedin an amount of 100 mol %), or may be made of a solid solution ofstrontium titanate with lead titanate, PLZT, barium titanate, etc.

In the piezoelectric element of the present invention, it is preferredthat the first electrode layer is made of at least one noble metalselected from the group consisting of platinum, iridium, palladium andruthenium.

In this way, the first electrode layer is made of a material that iscapable of withstanding the temperatures at which various films of thepiezoelectric element are formed by a sputtering method, or the like,and that is suitable as an electrode material.

Moreover, in the piezoelectric element of the present invention, it ispreferred that an amount of additive to be added to the first electrodelayer is greater than zero and less than or equal to 20 mol %.

The amount of additive is preferably less than or equal to 20 mol %,because the crystallinity and the orientation of the orientation controllayer deteriorate when the amount of additive exceeds 20 mol %.

Furthermore, in the piezoelectric element of the present invention, itis preferred that the piezoelectric layer is made of a piezoelectricmaterial whose main component is lead zirconate titanate.

By using such a piezoelectric material having desirable piezoelectriccharacteristics, it is possible to obtain a high-performancepiezoelectric element.

Moreover, in the piezoelectric element of the present invention, it ispreferred that the first electrode layer is provided on a substrate; andan adhesive layer for improving adhesion between the substrate and thefirst electrode layer is provided between the substrate and the firstelectrode layer.

In this way, it is possible to improve the adhesion between thesubstrate and the first electrode layer, thereby preventing peeling offduring the manufacture of the piezoelectric element.

A first ink jet head of the present invention includes: a piezoelectricelement in which a first electrode layer, a piezoelectric layer and asecond electrode layer are layered in this order; a vibration layerprovided on one surface of the piezoelectric element that is closer tothe second electrode layer; and a pressure chamber member bonded to onesurface of the vibration layer that is away from the piezoelectricelement and including a pressure chamber for storing ink therein, inwhich the vibration layer is displaced in a thickness direction by apiezoelectric effect of the piezoelectric layer of the piezoelectricelement so as to discharge the ink out of the pressure chamber, wherein:the first electrode layer of the piezoelectric element is made of anoble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added; and thepiezoelectric layer is made of a rhombohedral or tetragonal perovskiteoxide that is preferentially oriented along a (001) plane.

Thus, by forming the first electrode layer, the piezoelectric layer, thesecond electrode layer and the vibration layer in this order on thesubstrate by a sputtering method, or the like, and removing thesubstrate after bonding the pressure chamber member to the vibrationlayer, it is possible to obtain an ink jet head with a piezoelectricelement having a similar structure to that of the piezoelectric elementof the present invention, with the degree of (001) orientation of thepiezoelectric layer of the piezoelectric element being as high as 90% ormore. Therefore, it is possible to obtain an ink jet head with a smalldeviation in the ink-discharge performance and with a desirabledurability.

In the first ink jet head of the present invention, it is preferred thatan orientation control layer made of a cubic or tetragonal perovskiteoxide that is preferentially oriented along a (100) or (001) plane isprovided between the first electrode layer and the piezoelectric layerof the piezoelectric element.

Thus, by forming the first electrode layer, the orientation controllayer, the piezoelectric layer, the second electrode layer and thevibration layer in this order on the substrate by a sputtering method,or the like, and removing the substrate after bonding the pressurechamber member to the vibration layer, it is possible to obtain an inkjet head with a stable ink-discharge performance and with a desirabledurability.

A second ink jet head of the present invention includes: a piezoelectricelement in which a first electrode layer, a piezoelectric layer and asecond electrode layer are layered in this order; a vibration layerprovided on one surface of the piezoelectric element that is closer tothe first electrode layer; and a pressure chamber member bonded to onesurface of the vibration layer that is away from the piezoelectricelement and including a pressure chamber for storing ink therein, inwhich the vibration layer is displaced in a thickness direction by apiezoelectric effect of the piezoelectric layer of the piezoelectricelement so as to discharge the ink out of the pressure chamber, wherein:the first electrode layer of the piezoelectric element is made of anoble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added; and thepiezoelectric layer is made of a rhombohedral or tetragonal perovskiteoxide that is preferentially oriented along a (001) plane.

Thus, by using the pressure chamber member as a substrate, and formingthe vibration layer, the first electrode layer, the piezoelectric layerand the second electrode layer in this order on the pressure chambermember by a sputtering method, or the like, it is possible to obtain anink jet head with similar functions and effects to those of the firstink jet head of the present invention.

In the second ink jet head of the present invention, it is preferredthat an orientation control layer made of a cubic or tetragonalperovskite oxide that is preferentially oriented along a (100) or (001)plane is provided between the first electrode layer and thepiezoelectric layer of the piezoelectric element.

Thus, by using the pressure chamber member as a substrate, and formingthe vibration layer, the first electrode layer, the orientation controllayer, the piezoelectric layer and the second electrode layer in thisorder on the pressure chamber member by a sputtering method, or thelike, it is possible to obtain an ink jet head with similar functionsand effects to those of the first ink jet head of the present inventionand with an orientation control layer provided in the piezoelectricelement.

An angular velocity sensor of the present invention includes a substrateincluding a fixed portion and at least a pair of vibrating portionsextending from the fixed portion in a predetermined direction, in whicha first electrode layer, a piezoelectric layer and a second electrodelayer are layered in this order at least on each of the vibratingportions of the substrate, and the second electrode layer on each of thevibrating portions is patterned into at least one driving electrode forvibrating the vibrating portion in a width direction thereof and atleast one detection electrode for detecting a displacement of thevibrating portion in a thickness direction thereof, wherein: the firstelectrode layer is made of a noble metal to which at least one additiveselected from the group consisting of Mg, Ca, Sr, Ba, Al and oxidesthereof is added; and the piezoelectric layer is made of a rhombohedralor tetragonal perovskite oxide that is preferentially oriented along a(001) plane.

Each vibrating portion of the substrate is vibrated in the widthdirection thereof by applying a voltage between the driving electrode ofthe second electrode layer and the first electrode layer. When thevibrating portion deforms in the thickness direction due to the Coriolisforce while it is being vibrated, a voltage is generated between thedetection electrode of the second electrode layer and the firstelectrode layer, whereby the angular velocity can be calculated based onthe magnitude of the voltage (the Coriolis force). The portion fordetecting the angular velocity (the vibrating portion) is apiezoelectric element similar to the piezoelectric element of thepresent invention. Therefore, the piezoelectric constant can beincreased to be about 40 times as large as that of a conventionalangular velocity sensor using quartz, and thus the size thereof can bereduced significantly. Moreover, even if the angular velocity sensorsare mass-produced industrially, it is possible to obtain angularvelocity sensors with a high characteristics reproducibility and a smallcharacteristics deviation, and with a high breakdown voltage and a highreliability.

In the angular velocity sensor of the present invention, it is preferredthat an orientation control layer made of a cubic or tetragonalperovskite oxide that is preferentially oriented along a (100) or (001)plane is provided between the first electrode layer and thepiezoelectric layer.

A method for manufacturing the piezoelectric element of the presentinvention includes the steps of: forming a first electrode layer made ofa noble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added on asubstrate by a sputtering method; forming a piezoelectric layer made ofa rhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane on the first electrode layer by asputtering method; and forming a second electrode layer on thepiezoelectric layer.

In this way, it is possible to easily manufacture the piezoelectricelement of the present invention.

Alternatively, a method for manufacturing the piezoelectric element ofthe present invention includes the steps of: forming a first electrodelayer made of a noble metal to which at least one additive selected fromthe group consisting of Mg, Ca, Sr, Ba, Al and oxides thereof is addedon a substrate by a sputtering method; forming an orientation controllayer made of a cubic or tetragonal perovskite oxide that ispreferentially oriented along a (100) or (001) plane on the firstelectrode layer by a sputtering method; forming a piezoelectric layermade of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane on the orientation controllayer by a sputtering method; and forming a second electrode layer onthe piezoelectric layer.

In this way, it is possible to easily manufacture a piezoelectricelement in which an orientation control layer is provided between thefirst electrode layer and the piezoelectric layer.

A method for manufacturing the first ink jet head of the presentinvention includes the steps of: forming the first electrode layer madeof a noble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added on asubstrate by a sputtering method; forming the piezoelectric layer madeof a rhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane on the first electrode layer by asputtering method; forming the second electrode layer on thepiezoelectric layer; forming the vibration layer on the second electrodelayer; bonding a pressure chamber member for forming the pressurechamber on one surface of the vibration layer that is away from thesecond electrode layer; and removing the substrate after the bondingstep.

In this way, it is possible to easily manufacture the first ink jet headof the present invention.

Alternatively, a method for manufacturing the first ink jet head of thepresent invention includes the steps of: forming the first electrodelayer made of a noble metal to which at least one additive selected fromthe group consisting of Mg, Ca, Sr, Ba, Al and oxides thereof is addedon a substrate by a sputtering method; forming the orientation controllayer made of a cubic or tetragonal perovskite oxide that ispreferentially oriented along a (100) or (001) plane on the firstelectrode layer by a sputtering method; forming the piezoelectric layermade of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane on the orientation controllayer by a sputtering method; forming the second electrode layer on thepiezoelectric layer; forming the vibration layer on the second electrodelayer; bonding a pressure chamber member for forming the pressurechamber on one surface of the vibration layer that is away from thesecond electrode layer; and removing the substrate after the bondingstep.

In this way, it is possible to easily manufacture the first ink jet headof the present invention, in which the orientation control layer isprovided in the piezoelectric element.

A method for manufacturing the second ink jet head of the presentinvention includes the steps of: forming the vibration layer on apressure chamber substrate for forming the pressure chamber; forming thefirst electrode layer made of a noble metal to which at least oneadditive selected from the group consisting of Mg, Ca, Sr, Ba, Al andoxides thereof is added on the vibration layer by a sputtering method;forming the piezoelectric layer made of a rhombohedral or tetragonalperovskite oxide that is preferentially oriented along a (001) plane onthe first electrode layer by a sputtering method; forming the secondelectrode layer on the piezoelectric layer; and forming the pressurechamber in the pressure chamber substrate.

In this way, it is possible to easily manufacture the second ink jethead of the present invention.

Alternatively, a method for manufacturing the second ink jet head of thepresent invention includes the steps of: forming the vibration layer ona pressure chamber substrate for forming the pressure chamber; formingthe first electrode layer made of a noble metal to which at least oneadditive selected from the group consisting of Mg, Ca, Sr, Ba, Al andoxides thereof is added on the vibration layer by a sputtering method;forming the orientation control layer made of a cubic or tetragonalperovskite oxide that is preferentially oriented along a (100) or (001)plane on the first electrode layer by a sputtering method; forming thepiezoelectric layer made of a rhombohedral or tetragonal perovskiteoxide that is preferentially oriented along a (001) plane on theorientation control layer by a sputtering method; forming the secondelectrode layer on the piezoelectric layer; and forming the pressurechamber in the pressure chamber substrate.

In this way, it is possible to easily manufacture the second ink jethead of the present invention, in which the orientation control layer isprovided in the piezoelectric element.

A method for manufacturing the angular velocity sensor of the presentinvention includes the steps of: forming the first electrode layer madeof a noble metal to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added on thesubstrate by a sputtering method; forming the piezoelectric layer madeof a rhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane on the first electrode layer by asputtering method; forming the second electrode layer on thepiezoelectric layer; patterning the second electrode layer so as to formthe driving electrode and the detection electrode; patterning thepiezoelectric layer and the first electrode layer; and patterning thesubstrate so as to form the fixed portion and the vibrating portions.

In this way, it is possible to easily manufacture the angular velocitysensor of the present invention.

Alternatively, a method for manufacturing the angular velocity sensor ofthe present invention includes the steps of: forming the first electrodelayer made of a noble metal to which at least one additive selected fromthe group consisting of Mg, Ca, Sr, Ba, Al and oxides thereof is addedon the substrate by a sputtering method; forming the orientation controllayer made of a cubic or tetragonal perovskite oxide that ispreferentially oriented along a (100) or (001) plane on the firstelectrode layer by a sputtering method; forming the piezoelectric layermade of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane on the orientation controllayer by a sputtering method; forming the second electrode layer on thepiezoelectric layer; patterning the second electrode layer so as to formthe driving electrode and the detection electrode; patterning thepiezoelectric layer, the orientation control layer and the firstelectrode layer; and patterning the substrate so as to form the fixedportion and the vibrating portions.

In this way, it is possible to easily manufacture the angular velocitysensor of the present invention, in which the orientation control layeris provided in the portion for detecting the angular velocity.

A first ink jet recording apparatus of the present invention includes anink jet head, the ink jet head including: a piezoelectric element inwhich a first electrode layer, a piezoelectric layer and a secondelectrode layer are layered in this order; a vibration layer provided onone surface of the piezoelectric element that is closer to the secondelectrode layer; and a pressure chamber member bonded to one surface ofthe vibration layer that is away from the piezoelectric element andincluding a pressure chamber for storing ink therein, the ink jet headbeing capable of being relatively moved with respect to a recordingmedium, in which while the ink jet head is moved with respect to therecording medium, the vibration layer is displaced in a thicknessdirection by a piezoelectric effect of the piezoelectric layer of thepiezoelectric element in the ink jet head so as to discharge the ink outof the pressure chamber through a nozzle hole communicated to thepressure chamber onto the recording medium, thereby recordinginformation, wherein: the first electrode layer of the piezoelectricelement in the ink jet head is made of a noble metal to which at leastone additive selected from the group consisting of Mg, Ca, Sr, Ba, Aland oxides thereof is added; and the piezoelectric layer is made of arhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane.

A second ink jet recording apparatus of the present invention includesan ink jet head, the ink jet head including: a piezoelectric element inwhich a first electrode layer, a piezoelectric layer and a secondelectrode layer are layered in this order; a vibration layer provided onone surface of the piezoelectric element that is closer to the firstelectrode layer; and a pressure chamber member bonded to one surface ofthe vibration layer that is away from the piezoelectric element andincluding a pressure chamber for storing ink therein, the ink jet headbeing capable of being relatively moved with respect to a recordingmedium, in which while the ink jet head is moved with respect to therecording medium, the vibration layer is displaced in a thicknessdirection by a piezoelectric effect of the piezoelectric layer of thepiezoelectric element in the ink jet head so as to discharge the ink outof the pressure chamber through a nozzle hole communicated to thepressure chamber onto the recording medium, thereby recordinginformation, wherein: the first electrode layer of the piezoelectricelement in the ink jet head is made of a noble metal to which at leastone additive selected from the group consisting of Mg, Ca, Sr, Ba, Aland oxides thereof is added; and the piezoelectric layer is made of arhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane.

The first and second ink jet recording apparatuses of the presentinvention both provide a quite desirable printing performance anddurability.

In the first and second ink jet recording apparatuses of the presentinvention, it is preferred that an orientation control layer made of acubic or tetragonal perovskite oxide that is preferentially orientedalong a (100) or (001) plane is provided between the first electrodelayer and the piezoelectric layer of the piezoelectric element in theink jet head.

In this way, it is possible to stably and easily obtain an ink jetrecording apparatus that provides a quite desirable printing performanceand durability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a piezoelectric elementaccording to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically illustratingthe structure of an orientation control layer in the piezoelectricelement of FIG. 1.

FIG. 3 is a cross-sectional view illustrating another piezoelectricelement according to an embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view schematically illustratingthe structure of a piezoelectric layer of the piezoelectric element ofFIG. 3.

FIG. 5 is a perspective view illustrating the general structure of anink jet head according to an embodiment of the present invention.

FIG. 6 is an exploded perspective view illustrating an important part ofa pressure chamber member and an actuator section of the ink jet head ofFIG. 5.

FIG. 7 is a cross-sectional view illustrating an important part of apressure chamber member and an actuator section of the ink jet head ofFIG. 5.

FIG. 8A to FIG. 8C illustrate a deposition step, a step of formingpressure chamber cavities, and an adhesive application step,respectively, in a method for manufacturing the ink jet head of FIG. 5.

FIG. 9A and FIG. 9B illustrate a step of bonding a substrate after thedeposition process and the pressure chamber member to each other, and astep of forming vertical walls, respectively, in the method formanufacturing the ink jet head of FIG. 5.

FIG. 10A and FIG. 10B illustrate a step of removing a substrate (fordepositing films thereon) and an adhesive layer, and a step of dividinga first electrode layer, respectively, in the method for manufacturingthe ink jet head of FIG. 5.

FIG. 11A and FIG. 11B illustrate a step of dividing the orientationcontrol layer and the piezoelectric layer, and a step of cutting off asubstrate (for forming the pressure chamber member), respectively, inthe method for manufacturing the ink jet head of FIG. 5.

FIG. 12A to FIG. 12D illustrate a step of producing an ink channelmember and a nozzle plate, a step of bonding the ink channel member andthe nozzle plate to each other, a step of bonding the pressure chambermember and the ink channel member to each other, and a completed ink jethead, respectively, in the method for manufacturing the ink jet head ofFIG. 5.

FIG. 13 is a plan view illustrating how Si substrates on which filmshave been deposited are bonded to an Si substrate for forming thepressure chamber member in the method for manufacturing the ink jet headof FIG. 5.

FIG. 14 is a cross-sectional view illustrating an important part of apressure chamber member and an actuator section in another ink jet headaccording to an embodiment of the present invention.

FIG. 15A and FIG. 15B illustrate a deposition step, and a step offorming a pressure chamber, respectively, in a method for manufacturingthe ink jet head of FIG. 14.

FIG. 16 is a schematic perspective view illustrating an ink jetrecording apparatus according to an embodiment of the present invention.

FIG. 17 is a schematic perspective view illustrating an angular velocitysensor according to an embodiment of the present invention.

FIG. 18 is a cross-sectional view taken along line XVIII-XVIII of FIG.17.

FIG. 19A to FIG. 19F illustrate a method for manufacturing the angularvelocity sensor of FIG. 17.

FIG. 20 is a plan view illustrating the method for manufacturing theangular velocity sensor after a second electrode layer is patterned.

FIG. 21 is a schematic perspective view illustrating a conventionalangular velocity sensor using quartz.

FIG. 22 is a cross-sectional view taken along line XXII-XXII of FIG. 21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings.

Embodiment 1

FIG. 1 illustrates a piezoelectric element according to an embodiment ofthe present invention. In the figure, the reference numeral 11 denotes asubstrate made of a 4-inch silicon (Si) wafer having a thickness of 0.3mm, and an adhesive layer 12 made of titanium (Ti) and having athickness of 0.02 μm is formed on the substrate 11. Note that thesubstrate 11 is not limited to an Si substrate, but may alternatively bea glass substrate, a metal substrate, a ceramic substrate, or the like.

A first electrode layer 14 having a thickness of 0.22 μm and made ofplatinum (Pt) to which 3.2 mol % of Sr is added is formed on theadhesive layer 12. The first electrode layer 14 is oriented along the(111) plane.

An orientation control layer 15 made of PLT having a cubic or tetragonalperovskite crystalline structure whose lanthanum (La) content is 10 mol% and whose lead content is 8 mol % in excess of the stoichiometriccomposition is formed on the first electrode layer 14. The orientationcontrol layer 15 is preferentially oriented along the (100) or (001)plane, and has a thickness of 0.03 μm. Note that the thickness of theorientation control layer 15 is not limited to any particular thicknessas long as it is in the range of 0.01 to 0.2 μm.

A piezoelectric layer 16 having a thickness of 3 μm and made of PZThaving a rhombohedral or tetragonal perovskite crystalline structure isformed on the orientation control layer 15. The piezoelectric layer 16is preferentially oriented along the (001) plane. The Zr/Ti compositionof the PZT material is 53/47, which is near the boundary between beingtetragonal and being rhombohedral (i.e., the morphotropic phaseboundary). Note that the Zr/Ti composition of the piezoelectric layer 16is not limited to 53/47, but may be any other suitable composition aslong as it is in the range of 30/70 to 70/30. Moreover, the material ofthe piezoelectric layer 16 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used. Furthermore, the thickness thereofis not limited to any particular thickness as long as it is in the rangeof 0.5 to 5.0 μm.

A second electrode layer 17 having a thickness of 0.2 μm and made of Ptis formed on the piezoelectric layer 16. Note that the material of thesecond electrode layer 17 is not limited to Pt as long as it is aconductive material, and the thickness thereof is not limited to anyparticular thickness as long as it is in the range of 0.1 to 0.4 μm.

The piezoelectric element is obtained by depositing the adhesive layer12, the first electrode layer 14, the orientation control layer 15, thepiezoelectric layer 16 and the second electrode layer 17 in this orderon the substrate 11 by a sputtering method. Note that the depositionmethod is not limited to a sputtering method, but may alternatively beany other suitable deposition method as long as a crystalline thin filmis directly formed without the crystallization step using a heattreatment (e.g., a CVD method). Moreover, the deposition method for theadhesive layer 12 and the second electrode layer 17 may be a sol-gelmethod, or the like.

The adhesive layer 12 is provided for improving the adhesion between thesubstrate 11 and the first electrode layer 14. The material of theadhesive layer 12 is not limited to Ti, but may alternatively betantalum, iron, cobalt, nickel, chromium, or a compound thereof(including Ti). Moreover, the thickness thereof is not limited to anyparticular thickness as long as it is in the range of 0.005 to 1 μm. Theadhesive layer 12 is not always necessary, and the first electrode layer14 may alternatively be formed directly on the substrate 11.

The first electrode layer 14 not only functions as an electrode, butalso functions, with the addition of Sr, to preferentially orient theorientation control layer 15 along the (100) or (001) plane. Theadditive used for such a function is not limited to Sr, but mayalternatively be at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof The amount of theadditive to be added is preferably greater than zero and less than orequal to 20 mol %. Moreover, the material of the first electrode layer14 may be at least one noble metal selected from the group consisting ofPt, iridium, palladium and ruthenium, and the thickness thereof is notlimited to any particular thickness as long as it is in the range of0.05 to 2 μm.

The orientation control layer 15 is provided for improving thecrystallinity and the (001) orientation property of the piezoelectriclayer 16. For this purpose, the orientation control layer 15 is made ofPLT, which contains La and contains no Zr and whose lead content is inexcess of the stoichiometric composition. Note that in order to improvethe crystallinity and the orientation of the piezoelectric layer 16, theLa content thereof may be greater than zero and less than or equal to 30mol %, and the lead content thereof may be in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %. Moreover, the material of the orientation controllayer 15 is not limited to PLT as described above, but may alternativelybe PLZT obtained by adding zirconium to PLT, or may be a materialobtained by adding at least one of magnesium and manganese to PLT orPLZT. The zirconium content is preferably less than or equal to 20 mol%, and when at least one of magnesium and manganese is added, the totalamount thereof to be added is preferably greater than zero and less thanor equal to 10 mol % (the amount of one of magnesium and manganese maybe zero). Moreover, in order to improve the crystallinity and the (001)orientation property of the piezoelectric layer 16, the orientationcontrol layer 15 may alternatively be made of a strontium-containingperovskite oxide, which can be formed at lower temperatures than PZT, orthe like. In such a case, it is particularly preferred that strontiumtitanate (SrTiO₃) is contained, and the strontium titanate content maybe equal to or greater than 5 mol % and less than or equal to 100 mol %,i.e., only strontium titanate may be contained (in an amount of 100 mol%). Alternatively, lead titanate, PLZT, barium titanate, or the like,may be contained in addition to strontium titanate to form a solidsolution with strontium titanate.

In the vicinity of one surface of the orientation control layer 15 thatis closer to the first electrode layer 14, a (100)- or (001)-orientedregion 15 a extends over Sr located on one surface of the firstelectrode layer 14 that is closer to the orientation control layer 15,as illustrated in FIG. 2, so that the cross-sectional area of the region15 a in the direction perpendicular to the thickness direction graduallyincreases in the direction away from the first electrode layer 14 towardthe piezoelectric layer 16. On the other hand, since the first electrodelayer 14 is oriented along the (111) plane, each region 15 b of theorientation control layer 15, which is located over a portion of thesurface of the first electrode layer 14 where Sr does not exist, is notoriented along the (100) or (001) plane, but is oriented along the (111)plane in the present embodiment (the region 15 b may be oriented in adirection other than along the (111) plane or may be amorphous dependingon the material of the first electrode layer 14). Such a region 15 bthat is not oriented along the (100) or (001) plane extends only withina distance of about 20 nm at maximum from the surface of the orientationcontrol layer 15 that is closer to the first electrode layer 14. If thethickness of the orientation control layer 15 is 0.02 μm or more, the(100)- or (001)-oriented region 15 a extends substantially across theentire surface of the orientation control layer 15 that is closer to thepiezoelectric layer 16.

The piezoelectric layer 16 is preferentially oriented along the (001)plane by the orientation control layer 15, and the degree of (001)orientation, α, of the piezoelectric layer 16 is 90% or more.

Note that it is not necessary that the region 15 a extends substantiallyacross the entire surface of the orientation control layer 15 that iscloser to the piezoelectric layer 16. If the thickness of theorientation control layer 15 is less than 0.02 μm, the region 15 b thatis not oriented along the (100) or (001) plane may exist partially.However, even in such a case, if the thickness of the orientationcontrol layer 15 is 0.01 μm or more, a (100)- or (001)-oriented regionextends across a major portion of the surface of the orientation controllayer 15 that is closer to the piezoelectric layer 16, with the degreeof (001) orientation of the piezoelectric layer 16 being as high as 90%or more.

Next, a method for manufacturing a piezoelectric element as describedabove will be described.

The adhesive layer 12, the first electrode layer 14, the orientationcontrol layer 15, the piezoelectric layer 16 and the second electrodelayer 17 are deposited in this order on the Si substrate 11 by asputtering method.

The adhesive layer 12 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate 11 to 400° C. in an argon gas at 1 Pa.

The first electrode layer 14 is obtained by using a Pt alloy targetcontaining 3 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate 11 to 500° C. in anargon gas at 1 Pa. Sr exists in a dotted pattern on one surface of theobtained first electrode layer 14 that is away from the adhesive layer12.

The orientation control layer 15 is obtained by using a sinter targetprepared by adding a 12 mol % excess of lead oxide (PbO) to PLTcontaining 13 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the substrate 11 to 600° C.in a mixed atmosphere of argon and oxygen (gas volume ratio:Ar:O₂=19:1)at a degree of vacuum of 0.8 Pa.

In this way, the orientation control layer 15 grows using Sr, whichexists in a dotted pattern on one surface of the first electrode layer14 that is closer to the orientation control layer 15, as a nucleus,whereby the orientation control layer 15 is likely to be oriented alongthe (100) or (001) plane over Sr. Since Sr is easily oxidized, even ifSr is not added in the form of an oxide, Sr existing in a dotted patternon the surface of the orientation control layer 15 is turned intostrontium oxide by oxygen introduced when forming the orientationcontrol layer 15. Therefore, since strontium oxide is an NaCl-type oxidehaving the same crystalline structure as that of an MgO substrate, theorientation control layer 15 grows over Sr (strontium oxide) while usingit as a nucleus, whereby the orientation control layer 15 is likely tobe oriented along the (100) or (001) plane over Sr.

Note that Mg, Ca and Ba, which have been mentioned above as additives tothe first electrode layer 14, are alkaline-earth metals as is Sr, andthus are easily oxidized to form NaCl-type oxides. Therefore, with anyof these alternative additives, the orientation control layer 15 isgrown over the additive (oxide) using it as a nucleus, whereby theorientation control layer 15 is likely to be oriented along the (100) or(001) plane over the additive. Moreover, for Al, there is only one kindof oxide, Al₂O₃, which is a stable oxide. Therefore, by optimizing theconditions for forming the piezoelectric layer (when the piezoelectriclayer is formed by a sputtering method, for example, a mixed gas ofargon and oxygen is used while setting the oxygen partial pressure to berelatively small, e.g., 5% or less), the piezoelectric layer is grownover Al (aluminum oxide) using it as a nucleus and is stably orientedalong the (001) plane.

On the other hand, since the first electrode layer 14 is oriented alongthe (111) plane, regions of the orientation control layer 15 locatedover portions of the surface of the first electrode layer 14 where Srdoes not exist are not oriented along the (100) or (001) plane (but isoriented along the (111) plane in the present embodiment). However,since a (001)-oriented portion grows more easily in an oxygen-containingdeposition atmosphere, the (001)-oriented portion of the PLT film overSr grows at a higher rate. Therefore, the (001)-oriented portion growswhile gradually expanding in the lateral direction to form an invertedcone shape, and while suppressing the growth of crystal grains orientedalong the (111) plane, which grow at a lower rate. Thus, as the crystalgrowth process proceeds, the (100)- or (001)-oriented region graduallyexpands while the (111)-oriented region gradually shrinks. As a result,in the vicinity of the first electrode layer 14, the orientation controllayer 15 has the (100)- or (001)-oriented region 15 a (over Sr locatedon one surface of the first electrode layer 14 that is closer to theorientation control layer 15) and the region 15 b that is not orientedalong the (100) or (001) plane (over portions of the surface of thefirst electrode layer 14 where Sr does not exist), as described above.The cross-sectional area of the (100)- or (001)-oriented region 15 aincreases in the direction away from the first electrode layer 14 towardthe other side (i.e., toward the piezoelectric layer 16). When thethickness of the orientation control layer 15 is about 20 nm, the(001)-oriented region 15 a extends substantially across the entiresurface. Thus, if the thickness of the orientation control layer 15 is0.03 μm, the (100)- or (001)-oriented region 15 a extends substantiallyacross the entire surface of the orientation control layer 15 that iscloser to the piezoelectric layer 16.

The piezoelectric layer 16 is obtained by using a sinter target of PZT(Zr/Ti=53/47) and applying a high-frequency power of 250 W thereto for 3hours while heating the substrate 11 to 570° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa. Since the surface of the orientation control layer 15 that iscloser to the piezoelectric layer 16 is oriented along the (100) or(001) plane, the piezoelectric layer 16 is oriented along the (001)plane (herein Zr/Ti=53/47, and thus the crystal is rhombohedral; sincethe (100) plane and the (001) plane are the same in a rhombohedralsystem, the rhombohedral (100) orientation is included herein), wherebythe degree of (001) orientation thereof (the degree of (100) orientationof the rhombohedral system) is 90% or more. Moreover, since theorientation control layer 15 has a desirable crystallinity, thepiezoelectric layer 16 also has a desirable crystallinity.

The second electrode layer 17 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa.

Thus, in the present embodiment, the piezoelectric layer 16 having adesirable crystallinity and a desirable orientation can be obtained bydepositing it by a sputtering method on the inexpensive siliconsubstrate 11, without using an expensive MgO single-crystal substrate.Therefore, it is possible to suppress the deviation in the piezoelectriccharacteristics of the piezoelectric element and to improve thereliability thereof while reducing the manufacturing cost. Moreover,since the orientation control layer 15 contains no zirconium, a layer ofa low crystallinity made of a Zr oxide is less likely to be formed,whereby it is possible to increase the breakdown voltage of thepiezoelectric element.

Note that the orientation control layer 15 is not always necessary, andthe piezoelectric layer 16 may alternatively be formed directly on thefirst electrode layer 14 as illustrated in FIG. 3. In such a case, thepiezoelectric layer 16 grows over Sr using it as a nucleus so as to beoriented along the (001) plane over Sr, as does the orientation controllayer 15. In the vicinity of one surface of the piezoelectric layer 16that is closer to the first electrode layer 14, a (001)-oriented region16 a extends over Sr located on one surface of the first electrode layer14 that is closer to the piezoelectric layer 16, as illustrated in FIG.4, so that the cross-sectional area of the region 16 a in the directionperpendicular to the thickness direction gradually increases in thedirection away from the first electrode layer 14 toward the secondelectrode layer 17. On the other hand, each region 16 b of thepiezoelectric layer 16, which is located over a portion of the surfaceof the first electrode layer 14 where Sr does not exist, is not orientedalong the (001) plane, but is oriented along the (111) plane in thepresent embodiment (the region 16 b may be oriented in a direction otherthan along the (111) plane or may be amorphous depending on the materialof the first electrode layer 14). Such a region 16 b that is notoriented along the (001) plane extends only within a distance of about20 nm at maximum from the surface of the piezoelectric layer 16 that iscloser to the first electrode layer 14. When the thickness of thepiezoelectric layer 16 is about 20 nm, the (001)-oriented region 16 aextends substantially across the entire surface of the piezoelectriclayer 16. As a result, if the thickness of the piezoelectric layer isset to be 0.5 μm or more, it is possible to sufficiently obtain a degreeof (001) orientation of 90% or more.

Next, specific examples of the present invention will be described.

EXAMPLE 1

A piezoelectric element of Example 1 was produced by using the samematerial, thickness and manufacturing method for each film as those ofthe embodiment described above. No crack or peeling off was observed forany of the films of the piezoelectric element of Example 1.

The crystal orientation and the film composition of the piezoelectriclayer before the formation of the second electrode layer were examined.Specifically, an analysis by an X-ray diffraction method showed that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=97%). Moreover, ananalysis of the composition of the PZT film with an X-ray microanalyzershowed that the Zr/Ti ratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined. Specifically, an analysis by an X-ray diffraction methodshowed that the Pt film was oriented along the (111) plane. Moreover, ananalysis of the composition at a depth of 5 nm from the surface withX-ray photoelectron spectroscopy (XPS) showed that the Sr content was3.2 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined. The PLT film of the orientation control layer had a(100)-oriented perovskite crystalline structure. Note that a(111)-oriented region was observed on one side of the orientationcontrol layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where Sr does not exist. Moreover,a composition analysis with an X-ray microanalyzer showed that 10 mol %of lanthanum was contained, and an 8 mol % excess of Pb was contained.

Next, before the formation of the second electrode layer, 100cantilevers having a size of 15 mm×2 mm were cut out by dicing. Then,the second electrode layer having a thickness of 0.2 μm was formedthereon by a sputtering method, and the piezoelectric constant d31 wasmeasured (see, for example, Japanese Laid-Open Patent Publication No.2001-21052 for the method for measuring the piezoelectric constant d31).The average piezoelectric constant of the 100 cantilevers was −125 pC/N(deviation: σ=4.0%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.2 μm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. Note that the breakdown voltage value was defined to be the valueof the applied voltage for which the current value was 1 μA. As aresult, the average breakdown voltage value was 124 V (deviation:σ=4.1%).

EXAMPLE 2

In Example 2, a 4-inch stainless steel (SUS304) having a thickness of0.25 mm was used as the substrate, a tantalum (Ta) film having athickness of 0.01 μm was used as the adhesive layer, a Pt film having athickness of 0.25 μm and containing 9 mol % of strontium oxide was usedas the first electrode layer, a PLZT film having a thickness of 0.03 μmand containing 17 mol % of lanthanum and 10 mol % of zirconium in whichthe lead content was 6 mol % in excess of the stoichiometric compositionwas used as the orientation control layer, a PZT film (Zr/Ti=40/60)having a thickness of 2.8 μm was used as the piezoelectric layer, and aPt film having a thickness of 0.1 μm was used as the second electrodelayer.

The adhesive layer was obtained by using a Ta target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate to 500° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using a Pt alloy targetcontaining 10 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=15:1).

The orientation control layer was obtained by using a sinter target,which was prepared by adding a 10 mol % excess of lead oxide (PbO) toPLZT 20 mol % of lanthanum and 10 mol % of zirconium, and applying ahigh-frequency power of 300 W thereto for 15 minutes at a substratetemperature of 600° C. in a mixed atmosphere of argon and oxygen (gasvolume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=40/60) and applying a high-frequency power of 250 W thereto for 3hours at a substrate temperature of 590° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained as in Example 1 (but with adifferent process time).

Also in Example 2, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined as in Example 1, indicatingthat the piezoelectric layer had a (001)-oriented tetragonal perovskitecrystalline structure (degree of (001) orientation: α=98%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 40/60 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the strontium oxide content was 9 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the film had a (001)-orientedperovskite crystalline structure.

Note that a (111)-oriented region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the (111)-oriented region exists over a portion ofthe surface of the first electrode layer where strontium oxide does notexist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.1 μm), indicating that the average piezoelectric constant was −132pC/N (deviation: σ=2.5%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.1 μm),indicating that the average breakdown voltage value was 130 V(deviation: σ=4.4%).

EXAMPLE 3

In Example 3, a barium borosilicate glass having a thickness of 0.5 mm(size: 100 mm×100 mm) was used as the substrate, a nickel (Ni) filmhaving a thickness of 0.005 μm was used as the adhesive layer, aniridium (Ir) film having a thickness of 0.15 μm and containing 18 mol %of Ca was used as the first electrode layer, a film having a thicknessof 0.02 μm and made of a solid solution of strontium titanate containing18 mol % of Sr and PZT containing 15 mol % of Zr in which the leadcontent was 16 mol % in excess of the stoichiometric composition wasused as the orientation control layer, a PZT film (Zr/Ti=60/40) having athickness of 2.5 μm was used as the piezoelectric layer, and a Pt filmhaving a thickness of 0.01 μm was used as the second electrode layer.

The adhesive layer was obtained by using an Ni target and applying ahigh-frequency power of 200 W thereto for 1 minute while heating thesubstrate to 300° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using an Ir alloy targetcontaining 16 mol % of Ca and applying a high-frequency power of 200 Wthereto for 10 minutes while heating the substrate to 600° C. in anargon gas at 1 Pa.

The orientation control layer was obtained by using a sinter target madeof a solid solution of strontium titanate (the Sr content: 20 mol %) andPZT (prepared by setting the Zr content to 16 mol % and adding a 22 mol% excess of lead oxide (PbO)) and applying a high-frequency power of 300W thereto for 15 minutes at a substrate temperature of 580° C. in amixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1) at adegree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=60/40) and applying a high-frequency power of 260 W thereto for 3hours at a substrate temperature of 600° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained as in Example 1 (but with adifferent process time).

Also in Example 3, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=97%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 60/40 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Ca content was 18 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the film had a (100)-orientedperovskite crystalline structure.

Note that an amorphous region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the amorphous region exists over a portion of thesurface of the first electrode layer where Ca does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −125pC/N (deviation: σ=3.6%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 118 V(deviation: σ=5.2%).

EXAMPLE 4

In Example 4, a 4-inch silicon wafer having a thickness of 0.5 mm wasused as the substrate, a titanium film having a thickness of 0.01 μm wasused as the adhesive layer, an Ir film having a thickness of 0.25 μm andcontaining 5 mol % of magnesium oxide was used as the first electrodelayer, a PLT film having a thickness of 0.05 μm and containing 10 mol %of lanthanum in which the lead content was 10 mol % in excess of thestoichiometric composition was used as the orientation control layer, aPZT film (Zr/Ti=52/48) having a thickness of 3.2 μm was used as thepiezoelectric layer, and a Pt film having a thickness of 0.01 μm wasused as the second electrode layer.

The adhesive layer was obtained by using an Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate to 500° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using an Ir alloy targetcontaining 5 mol % of Mg and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 500° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=10:1).

The orientation control layer was obtained by using a sinter targetprepared by adding a 14 mol % excess of lead oxide (PbO) to PLTcontaining 10 mol % of lanthanum and applying a high-frequency power of300 W thereto for 20 minutes at a substrate temperature of 600° C. in amixed atmosphere of argon and oxygen (gas volume ratio:Ar:O₂=15:1) at adegree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 270 W thereto for 3hours at a substrate temperature of 620° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.4 Pa.

The second electrode layer was obtained as in Example 1 (but with adifferent process time).

Also in Example 4, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=98%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 52/48 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the magnesium oxide content was 5 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure.

Note that an amorphous region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the amorphous region exists over a portion of thesurface of the first electrode layer where magnesium oxide does notexist. Moreover, 10 mol % of lanthanum was contained, and a 10 mol %excess of Pb was contained.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −140pC/N (deviation: σ=2.4%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 121 V(deviation: σ=4.2%).

EXAMPLE 5

In Example 5, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, the first electrode layer was formed directly onthe substrate without providing the adhesive layer therebetween, a Ptfilm having a thickness of 0.22 μm and containing 1.8 mol % of Ba wasused as the first electrode layer, a film having a thickness of 0.03 μmand made of a solid solution of strontium titanate and barium titanate(strontium titanate content: 90 mol %) was used as the orientationcontrol layer, a PZT film (Zr/Ti=53/47) having a thickness of 3 μm wasused as the piezoelectric layer, and a Pt film having a thickness of 0.2μm was used as the second electrode layer.

The first electrode layer was obtained by using an Pt alloy targetcontaining 2 mol % of Ba and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in anargon gas at 1 Pa.

The orientation control layer was obtained by using a sinter target madeof a solid solution of strontium titanate and barium titanate (strontiumtitanate content: 90 mol %) and applying a high-frequency power of 300 Wthereto for 12 minutes at a substrate temperature of 650° C. in a mixedatmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1) at adegree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=53/47) and applying a high-frequency power of 250 W thereto for 3hours at a substrate temperature of 610° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained as in Example 1.

Also in Example 5, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=99%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Ba content was 1.8 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure.

Note that a (111)-oriented region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the (111)-oriented region exists over a portion ofthe surface of the first electrode layer where Ba does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −132 pC/N(deviation: σ=4.2%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 124 V (deviation: σ=4.1%).

EXAMPLE 6

In Example 6, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, a titanium film having a thickness of 0.02 μm wasused as the adhesive layer, a Pt film having a thickness of 0.21 μm andcontaining 3.6 mol % of Al was used as the first electrode layer, a PLTfilm having a thickness of 0.03 μm and containing 10 mol % of lanthanumin which the lead content was 8 mol % in excess of the stoichiometriccomposition was used as the orientation control layer, a PZT film(Zr/Ti=53/47) having a thickness of 3 μm was used as the piezoelectriclayer, and a Pt film having a thickness of 0.2 μm was used as the secondelectrode layer.

The first electrode layer was obtained by using a Pt alloy targetcontaining 4 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 380° C. in anargon gas at 1 Pa.

The adhesive layer, the orientation control layer, the piezoelectriclayer and the second electrode layer were obtained as in Example 1(except that the gas volume ratio between argon and oxygen was set to beAr:O₂=24:1 in the formation of the orientation control layer).

Also in Example 6, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (001)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: (α=98%). Moreover,an examination of the composition of the PZT film showed that the Zr/Tiratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Al content was 3.6 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the film had a (100)-orientedperovskite crystalline structure.

Note that a (111)-oriented region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the (111)-oriented region exists over a portion ofthe surface of the first electrode layer where Al does not exist.Moreover, 10 mol % of lanthanum was contained, and an 8 mol % excess ofPb was contained.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −127 pC/N(deviation: σ=4.1%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 125 V (deviation: σ=4.0%).

EXAMPLE 7

In Example 7, a 4-inch stainless steel (SUS304) having a thickness of0.25 mm was used as the substrate, a Ta film having a thickness of 0.01μm was used as the adhesive layer, a Pt film having a thickness of 0.25μm and containing 1.5 mol % of aluminum oxide was used as the firstelectrode layer, a PLZT film having a thickness of 0.03 μm andcontaining 17 mol % of lanthanum and 10 mol % of zirconium in which thelead content was 6 mol % in excess of the stoichiometric composition wasused as the orientation control layer, a PZT film (Zr/Ti=40/60) having athickness of 2.8 μm was used as the piezoelectric layer, and a Pt filmhaving a thickness of 0.1 μm was used as the second electrode layer.

The first electrode layer was obtained by using a Pt alloy targetcontaining 2 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=29:1).

The adhesive layer, the orientation control layer, the piezoelectriclayer and the second electrode layer were obtained as in Example 2(except that the gas volume ratio between argon and oxygen was set to beAr:O₂=24:1 and the degree of vacuum was set to be 0.9 Pa in theformation of the orientation control layer).

Also in Example 7, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (001)-oriented tetragonal perovskitecrystalline structure (degree of (001) orientation: α=97%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 40/60 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the aluminum oxide content was 1.5 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the film had a (001)-orientedperovskite crystalline structure.

Note that a (111)-oriented region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the (111)-oriented region exists over a portion ofthe surface of the first electrode layer where aluminum oxide does notexist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.1 μm), indicating that the average piezoelectric constant was −130pC/N (deviation: σ=2.6%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.1 μm),indicating that the average breakdown voltage value was 132 V(deviation: σ=4.4%).

EXAMPLE 8

In Example 8, a barium borosilicate glass having a thickness of 0.5 mm(size: 100 mm×100 mm) was used as the substrate, an Ni film having athickness of 0.005 μm was used as the adhesive layer, an Ir film havinga thickness of 0.15 μm and containing 18 mol % of Al was used as thefirst electrode layer, a film having a thickness of 0.02 μm and made ofa solid solution of strontium titanate containing 18 mol % of Sr and PZTcontaining 15 mol % of Zr in which the lead content was 16 mol % inexcess of the stoichiometric composition was used as the orientationcontrol layer, a PZT film (Zr/Ti=60/40) having a thickness of 2.5 μm wasused as the piezoelectric layer, and a Pt film having a thickness of0.01 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 20 mol % of Al and applying a high-frequency power of 200 Wthereto for 10 minutes while heating the substrate to 300° C. in anargon gas at 0.3 Pa.

The adhesive layer, the orientation control layer, the piezoelectriclayer and the second electrode layer were obtained as in Example 3(except that the substrate temperature was set to be 590° C., the gasvolume ratio between argon and oxygen was set to be Ar:O₂=29:1 and thedegree of vacuum was set to be 0.6 Pa in the formation of theorientation control layer, and the high-frequency power was set to be250 W in the formation of the piezoelectric layer).

Also in Example 8, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=97%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 60/40 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Al content was 18 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the film had a (100)-orientedperovskite crystalline structure.

Note that an amorphous region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the amorphous region exists over a portion of thesurface of the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −127pC/N (deviation: σ=3.6%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 120 V(deviation: σ=5.0%).

EXAMPLE 9

In Example 9, a 4-inch silicon wafer having a thickness of 0.5 mm wasused as the substrate, a Ti film having a thickness of 0.01 μm was usedas the adhesive layer, an Ir film having a thickness of 0.25 μm andcontaining 5 mol % of aluminum oxide was used as the first electrodelayer, a PLT film having a thickness of 0.05 μm and containing 10 mol %of lanthanum in which the lead content was 10 mol % in excess of thestoichiometric composition was used as the orientation control layer, aPZT film (Zr/Ti=52/48) having a thickness of 3.2 μm was used as thepiezoelectric layer, and a Pt film having a thickness of 0.01 μm wasused as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 6 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 500° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=29:1).

The adhesive layer, the orientation control layer, the piezoelectriclayer and the second electrode layer were obtained as in Example 4(except that the gas volume ratio between argon and oxygen was set to beAr:O₂=25:1 in the formation of the piezoelectric layer).

Also in Example 9, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=99%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 52/48 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the aluminum oxide content was 5 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure.

Note that an amorphous region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the amorphous region exists over a portion of thesurface of the first electrode layer where aluminum oxide does notexist. Moreover, 10 mol % of lanthanum was contained, and a 10 mol %excess of Pb was contained.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −141pC/N (deviation: σ=2.5%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 120 V(deviation: σ=4.4%).

EXAMPLE 10

In Example 10, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, the first electrode layer was formed directly onthe substrate without providing the adhesive layer therebetween, an Irfilm having a thickness of 0.22 μm and containing 1.8 mol % of Al wasused as the first electrode layer, a film having a thickness of 0.03 μmand made of a solid solution of strontium titanate and barium titanate(strontium titanate content: 90 mol %) was used as the orientationcontrol layer, a PZT film (Zr/Ti=53/47) having a thickness of 3 μm wasused as the piezoelectric layer, and a Pt film having a thickness of 0.2μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 2 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in anargon gas at 1 Pa.

The orientation control layer, the piezoelectric layer and the secondelectrode layer were obtained as in Example 5 (except that the substratetemperature was set to be 620° C., the gas volume ratio between argonand oxygen was set to be Ar:O₂=29:1 and the degree of vacuum was set tobe 0.5 Pa in the formation of the orientation control layer).

Also in Example 10, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=96%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Al content was 1.8 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure.

Note that a (111)-oriented region was observed on one side of theorientation control layer that is closer to the first electrode layer.It is believed that the (111)-oriented region exists over a portion ofthe surface of the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −133 pC/N(deviation: σ=4.0%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 120 V (deviation: σ=4.3%).

EXAMPLE 11

In Example 11, the piezoelectric layer was formed directly on the firstelectrode layer without providing the orientation control layertherebetween (this also applies to Examples 12 to 20 below), a 4-inchsilicon wafer having a thickness of 0.3 mm was used as the substrate, aTi film having a thickness of 0.02 μm was used as the adhesive layer, aPt film having a thickness of 0.22 μm to which 2.1 mol % of Sr was addedwas used as the first electrode layer, a PZT film (Zr/Ti=53/47) having athickness of 2.7 μm was used as the piezoelectric layer, and a Pt filmhaving a thickness of 0.2 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Pt alloy targetcontaining 2 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in anargon gas at 1 Pa.

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 1 (except that the substratetemperature was set to be 610° C. in the formation of the piezoelectriclayer).

Also in Example 11, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=98%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Sr content was 2.1 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where Sr does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −129 pC/N(deviation: σ=4.0%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 121 V (deviation: σ=4.3%).

EXAMPLE 12

In Example 12, a 4-inch stainless steel (SUS304) having a thickness of0.25 mm was used as the substrate, a tantalum (Ta) film having athickness of 0.01 μm was used as the adhesive layer, a Pt film having athickness of 0.25 μm and containing 8 mol % of strontium oxide was usedas the first electrode layer, a PZT film (Zr/Ti=40/60) having athickness of 2.7 μm was used as the piezoelectric layer, and a Pt filmhaving a thickness of 0.1 μm was used as the second electrode layer.

The first electrode layer was obtained by using a Pt alloy targetcontaining 8 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=15:1).

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 2 (except that the substratetemperature was set to be 600° C. in the formation of the piezoelectriclayer).

Also in Example 12, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (001)-oriented tetragonal perovskitecrystalline structure (degree of (001) orientation: α=97%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 40/60 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the strontium oxide content was 8 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where strontium oxide does notexist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.1 μm, indicating that the average piezoelectric constant was−124pC/N (deviation: σ=2.8%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.1 μm),indicating that the average breakdown voltage value was 119 V(deviation: σ=4.7%).

EXAMPLE 13

In Example 13, a barium borosilicate glass having a thickness of 0.5 mm(size: 100 mm×100 mm) was used as the substrate, an Ni film having athickness of 0.005 μm was used as the adhesive layer, an Ir film havinga thickness of 0.15 μm and containing 18 mol % of Mg was used as thefirst electrode layer, a PZT film (Zr/Ti=60/40) having a thickness of2.6 μm was used as the piezoelectric layer, and a Pt film having athickness of 0.01 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 19 mol % of Mg and applying a high-frequency power of 200 Wthereto for 10 minutes while heating the substrate to 600° C. in anargon gas at 1 Pa.

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 3 (except that the substratetemperature was set to be 580° C. in the formation of the piezoelectriclayer).

Also in Example 13, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=96%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 60/40 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Mg content was 18 mol %.

Note that an amorphous region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the amorphous region exists over a portion of the surfaceof the first electrode layer where Mg does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −123pC/N (deviation: σ=3.9%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 116 V(deviation: σ=5.2%).

EXAMPLE 14

In Example 14, a 4-inch silicon wafer having a thickness of 0.5 mm wasused as the substrate, a Ti film having a thickness of 0.01 μn was usedas the adhesive layer, an Ir film having a thickness of 0.25 μm andcontaining 5 mol % of calcium oxide was used as the first electrodelayer, a PZT film (Zr/Ti=52/48) having a thickness of 3.2 μm was used asthe piezoelectric layer, and a Pt film having a thickness of 0.01 μm wasused as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 5 mol % of Ca and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in a mixedatmosphere of argon and oxygen at 1 Pa (gas volume ratio: Ar:O₂=10:1).

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 4.

Also in Example 14, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=99%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 52/48 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Ir film was oriented along the (111)plane. Moreover, the calcium oxide content was 5 mol %.

Note that an amorphous region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the amorphous region exists over a portion of the surfaceof the first electrode layer where calcium oxide does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −140pC/N (deviation: σ=2.4%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 124 V(deviation: σ=4.1%).

EXAMPLE 15

In Example 15, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, the first electrode layer was formed directly onthe substrate without providing the adhesive layer therebetween, a Ptfilm having a thickness of 0.22 μm and containing 2.1 mol % of Ba wasused as the first electrode layer, a PZT film (Zr/Ti=53/47) having athickness of 3 μm was used as the piezoelectric layer, and a Pt filmhaving a thickness of 0.2 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Pt alloy targetcontaining 2 mol % of Ba and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in anargon gas at 1 Pa.

The piezoelectric layer and the second electrode layer were obtained asin Example 5. Also in Example 15, no crack or peeling off was observedfor any of the films of the piezoelectric element.

Then, the crystal orientation and the film composition of thepiezoelectric layer before the formation of the second electrode layerwere examined, indicating that the piezoelectric layer had a(100)-oriented rhombohedral perovskite crystalline structure (degree of(100) orientation: α=98%). Moreover, an examination of the compositionof the PZT film showed that the Zr/Ti ratio was 53/47 as in the targetcomposition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Ba content was 2.1 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where Ba does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant of the 100cantilevers was −131 pC/N (deviation: σ=4.1%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 122 V (deviation: σ=3.9%).

EXAMPLE 16

In Example 16, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, a Ti film having a thickness of 0.02 μm was usedas the adhesive layer, a Pt film having a thickness of 0.22 μm to which2.1 mol % of Al was added was used as the first electrode layer, a PZTfilm (Zr/Ti=53/47) having a thickness of 2.7 μm was used as thepiezoelectric layer, and a Pt film having a thickness of 0.2 μm was usedas the second electrode layer.

The first electrode layer was obtained by using an Pt alloy targetcontaining 2 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 450° C. in anargon gas at 0.5 Pa.

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 1 (except that the substratetemperature was set to be 420° C. in the formation of the adhesivelayer, and the substrate temperature was set to be 610° C., the gasvolume ratio between argon and oxygen was set to be Ar:O₂=29:1, and thedegree of vacuum was set to be 0.2 Pa in the formation of thepiezoelectric layer).

Also in Example 16, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=97%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Al content was 2.1 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of-the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −120 pC/N(deviation: σ=3.8%).

Then, the breakdown voltage was measured as in Example 1, indicatingthat the average breakdown voltage value was 131 V (deviation: σ=4.0%).

EXAMPLE 17

In Example 17, a 4-inch stainless steel (SUS304) having a thickness of0.25 mm was used as the substrate, a Ta film having a thickness of 0.015μm was used as the adhesive layer, a Pt film having a thickness of 0.24μm and containing 8 mol % of aluminum oxide was used as the firstelectrode layer, a PZT film (Zr/Ti=40/60) having a thickness of 2.7 μmwas used as the piezoelectric layer, a Pt film having a thickness of 0.1μm was used as the second electrode layer.

The first electrode layer was obtained by using a Pt alloy targetcontaining 8 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 450° C. in a mixedatmosphere of argon and oxygen at 1.5 Pa (gas volume ratio: Ar:O₂=25:1).

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 2 (except that the gas volume ratiobetween argon and oxygen was set to be Ar:O₂=29:1 in the formation ofthe piezoelectric layer).

Also in Example 17, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (001)-oriented tetragonal perovskitecrystalline structure (degree of (001) orientation: α=99%). Moreover, anexamination of the composition; of the PZT film showed that the Zr/Tiratio was 40/60 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the aluminum oxide content was 8.4 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where aluminum oxide does notexist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.1 μm), indicating that the average piezoelectric constant was −128pC/N (deviation: σ=2.9%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.1 μm),indicating that the average breakdown voltage value was 119 V(deviation: σ=4.7%).

EXAMPLE 18

In Example 18, a barium borosilicate glass having a thickness of 0.5 mm(size: 100 mm×100 mm) was used as the substrate, an Ni film having athickness of 0.005 μm was used as the adhesive layer, an Ir film havinga thickness of 0.15 μm and containing 17 mol % of Al was used as thefirst electrode layer, a PZT film (Zr/Ti=60/40) having a thickness of2.6 μm was used as the piezoelectric layer, and a Pt film having athickness of 0.01 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 20 mol % of Al and applying a high-frequency power of 200 Wthereto for 10 minutes while heating the substrate to 600° C. in anargon gas at 1 Pa.

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 3 (except that the substratetemperature was set to be 400° C. in the formation of the adhesivelayer, the substrate temperature was set to be 580° C. and the gasvolume ratio between argon and oxygen was set to be Ar:O₂=29:1 in theformation of the piezoelectric layer, and the high-frequency power wasset to be 210 W in the formation of the second electrode layer).

Also in Example 18, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: (α=95%). Moreover,an examination of the composition of the PZT film showed that the Zr/Tiratio was 60/40 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Al content was 17 mol %.

Note that an amorphous region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the amorphous region exists over a portion of the surfaceof the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −133pC/N (deviation: σ=3.7%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 114 V(deviation: σ=5.0%).

EXAMPLE 19

In Example 19, a 4-inch silicon wafer having a thickness of 0.5 mm wasused as the substrate, a Ti film having a thickness of 0.01 μm was usedas the adhesive layer, an Ir—Pd alloy film (Ir/Pd=80/20) having athickness of 0.25 μm and containing 5 mol % of Al was used as the firstelectrode layer, a PZT film (Zr/Ti=52/48) having a thickness of 3.2 μmwas used as the piezoelectric layer, and a Pt film having a thickness of0.01 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir—Pd alloy target(Ir/Pd=80/20) containing 5 mol % of Al and applying a high-frequencypower of 200 W thereto for 12 minutes while heating the substrate to400° C. in an argon atmosphere at 1 Pa.

The adhesive layer, the piezoelectric layer and the second electrodelayer were obtained as in Example 4 (except that the gas volume ratiobetween argon and oxygen was set to be Ar:O₂=29:1 in the formation ofthe piezoelectric layer).

Also in Example 19, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=99%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratio was 52/48 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Ir—Pd film was oriented along the (111)plane. Moreover, the Al content was 4.7 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was a Pt film having a thicknessof 0.01 μm), indicating that the average piezoelectric constant was −140pC/N (deviation: σ=2.3%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was a Pt film having a thickness of 0.01 μm),indicating that the average breakdown voltage value was 125 V(deviation: σ=4.0%).

EXAMPLE 20

In Example 20, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, the first electrode layer was formed directly onthe substrate without providing the adhesive layer therebetween, an Irfilm having a thickness of 0.22 μm and containing 2.1 mol % of Al wasused as the first electrode layer, a PZT film (Zr/Ti=53/47) having athickness of 3 μm was used as the piezoelectric layer, and an Ir filmhaving a thickness of 0.2 μm was used as the second electrode layer.

The first electrode layer was obtained by using an Ir alloy targetcontaining 2 mol % of Al and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate to 400° C. in anargon gas at 1 Pa.

The piezoelectric layer and the second electrode layer were obtained asin Example 5 (except that the gas volume ratio between argon and oxygenwas set to be Ar:O₂=29:1 and the degree of vacuum was set to be 0.2 Pain the formation of the piezoelectric layer).

Also in Example 20, no crack or peeling off was observed for any of thefilms of the piezoelectric element. Then, the crystal orientation andthe film composition of the piezoelectric layer before the formation ofthe second electrode layer were examined, indicating that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=98%). Moreover, anexamination of the composition of the PZT film showed that the Zr/Tiratios was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the piezoelectric layer wereexamined, indicating that the Pt film was oriented along the (111)plane. Moreover, the Al content was 2.1 mol %.

Note that a (111)-oriented region was observed on one side of thepiezoelectric layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where Al does not exist.

Then, the piezoelectric constant d31 was measured as in Example 1(except that the second electrode layer was an Ir film having athickness of 0.2 μm), indicating that the average piezoelectric constantof the 100 cantilevers was −133 pC/N (deviation: σ=4.2%).

Then, the breakdown voltage was measured as in Example 1 (except thatthe second electrode layer was an Ir film having a thickness of 0.2 μm),indicating that the average breakdown voltage value was 122 V(deviation: σ=3.7%).

COMPARATIVE EXAMPLE 1

Comparative Example 1 is similar to Example 11 or 16 except for theaddition to the Pt film of the first electrode layer. As in Example 11or 16, the adhesive layer, the first electrode layer, the piezoelectriclayer and the second electrode layer are formed in this order on thesubstrate. A Pt film having a thickness of 0.22 μm and containing 2.1mol % of Ti was used as the first electrode layer. The first electrodelayer was obtained by using a Ti target and a Pt target and applyinghigh-frequency powers of 85 W and 200 W thereto, respectively, for 12minutes while heating the substrate to 400° C. in an argon gas at 1 Pa,using a multi-target sputtering apparatus.

The piezoelectric layer of the piezoelectric element of ComparativeExample 1 had a (100)-oriented rhombohedral perovskite crystallinestructure (degree of (100) orientation: α=31%).

Moreover, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −72 pC/N(deviation: σ=11.5%).

Furthermore, the breakdown voltage was measured as in Example 1,indicating that the average breakdown voltage value was 65 V (deviation:σ=14.5%).

COMPARATIVE EXAMPLE 2

Comparative Example 2 is similar to Comparative Example 1 except thatthe substrate temperature was set to be 410° C. in the formation of thefirst electrode layer.

The piezoelectric layer of the piezoelectric element of ComparativeExample 2 had a (100)-oriented rhombohedral perovskite crystallinestructure (degree of (100) orientation: α=30%).

Moreover, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −75 pC/N(deviation: σ=11.8%).

Furthermore, the breakdown voltage was measured as in Example 1,indicating that the average breakdown voltage value was 65 V (deviation:σ=14.1%).

COMPARATIVE EXAMPLE 3

Comparative Example 3 is also similar to Comparative Example 1 exceptthat the thickness of the first electrode layer was set to be 2.5 μm andthe amount of Ti to be added was set to be 2.5 mol %.

The piezoelectric layer of the piezoelectric element of ComparativeExample 4 had a (100)-oriented rhombohedral perovskite crystallinestructure (degree of (100) orientation: α=34%).

Moreover, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −70 pC/N(deviation: σ=11.7%).

Furthermore, the breakdown voltage was measured as in Example 1,indicating that the average breakdown voltage value was 68 V (deviation:σ=14.0%).

Thus, only by providing the piezoelectric layer on a Pt film to whichSr, Al, or the like, is added, via the orientation control layer, as inExamples 1 to 10, it is possible to improve the crystallinity and theorientation of the piezoelectric layer, and to improve the piezoelectriccharacteristics and the breakdown voltage of the piezoelectric element.Moreover, even if the orientation control layer is not provided, as inExamples 11 to 20, by providing the piezoelectric layer on a Pt film towhich Sr, Al, or the like, is added, it is possible to improve thecrystallinity and the orientation of the piezoelectric layer, and toimprove the piezoelectric characteristics and the breakdown voltage ofthe piezoelectric element.

Embodiment 2

FIG. 5 illustrates the general structure of an ink jet head according toan embodiment of the present invention, and FIG. 6 illustrates thestructure of an important part thereof In FIG. 5 and FIG. 6, thereference character A denotes a pressure chamber member. A pressurechamber cavity 101 is formed running through the pressure chamber memberA in the thickness direction (vertical direction) thereof The referencecharacter B denotes an actuator section placed so as to cover the upperopening of the pressure chamber cavity 101, and the reference characterC denotes an ink channel member placed so as to cover the lower openingof the pressure chamber cavity 101. Each pressure chamber cavity 101 ofthe pressure chamber member A is closed by the actuator section B andthe ink channel member C, placed on and under the pressure chambermember A, respectively, thereby forming a pressure chamber 102.

The actuator section B includes a first electrode layer 103 (separateelectrode) above each pressure chamber 102. The position of the firstelectrode layer 103 generally corresponds to that of the pressurechamber 102. As can be seen from FIG. 5, a large number of pressurechambers 102 and first electrode layers 103 are arranged in a staggeredpattern.

The ink channel member C includes a common ink chamber 105 shared by anumber of pressure chambers 102 arranged in the ink supply direction, asupply port 106 through which ink in the common ink chamber 105 issupplied into the pressure chamber 102, and an ink channel 107 throughwhich ink in the pressure chamber 102 is discharged.

The reference character D denotes a nozzle plate. The nozzle plate Dincludes nozzle holes 108 each of which is communicated to the inkchannel 107. Moreover, the reference character E denotes an IC chip. Avoltage is supplied from the IC chip E to each separate electrode 103via a bonding wire BW.

Next, the structure of the actuator section B will be described withreference to FIG. 7. FIG. 7 is a cross-sectional view taken along thedirection perpendicular to the ink supply direction shown in FIG. 5. Forthe purpose of illustration, FIG. 7 shows the pressure chamber member Aincluding four pressure chambers 102 arranged in the directionperpendicular to the ink supply direction. The actuator section Bincludes: the first electrode layers 103 each located above one pressurechamber 102 so that the position of the first electrode layer 103generally corresponds to that of the pressure chamber 102, anorientation control layer 104 provided on (under, as shown in thefigure) each first electrode layer 103, a piezoelectric layer 110provided on (under) the orientation control layer 104, a secondelectrode layer 112 (common electrode) provided on (under) thepiezoelectric layers 110 and shared by all the piezoelectric layers 110,a vibration layer 111 provided on (under) the second electrode layer112, which is displaced and vibrates in the thickness direction by thepiezoelectric effect of the piezoelectric layer 110, and an intermediatelayer 113 (vertical wall) provided on (under) the vibration layer 111and located above a partition wall 102 a for partitioning the pressurechambers 102 from one another. The first electrode layer 103, theorientation control layer 104, the piezoelectric layer 110 and thesecond electrode layer 112 are arranged in this order to form apiezoelectric element. Moreover, the vibration layer 111 is provided onone surface of the piezoelectric element that is closer to the secondelectrode layer 112.

Note that in FIG. 7, the reference numeral 114 denotes an adhesive forbonding the pressure chamber member A and the actuator section B to eachother. Therefore, even if a portion of the adhesive 114 runs out of thepartition wall 102 a in the adhesion process using the adhesive 114, theintermediate layer 113 functions to increase the distance between theupper surface of the pressure chamber 102 and the lower surface of thevibration layer 111 so that such a portion of the adhesive 114 does notattach to the vibration layer 111 and that the vibration layer 111 willbe displaced and vibrate as intended. Thus, it is preferred that thepressure chamber member A is bonded to one surface of the vibrationlayer 111 of the actuator section B that is away from the secondelectrode layer 112 via the intermediate layer 113 therebetween.However, the pressure chamber member A may alternatively be bondeddirectly to one surface of the vibration layer 111 that is away from thesecond electrode layer 112.

The materials of the first electrode layer 103, the orientation controllayer 104, the piezoelectric layer 110 and the second electrode layer112 are similar to those of the first electrode layer 14, theorientation control layer 15, the piezoelectric layer 16 and the secondelectrode layer 17, respectively, of Embodiment 1. Moreover, thestructures of the orientation control layer 104 and the piezoelectriclayer 110 are similar to those of the orientation control layer 15 andthe piezoelectric layer 16, respectively. In the vicinity of one surfaceof the orientation control layer 104 that is closer to the firstelectrode layer 103, a (100)- or (001)-oriented region extends over Srlocated on one surface of the first electrode layer 103 that is closerto the orientation control layer 104 so that the cross-sectional area ofsuch a region in the direction perpendicular to the thickness directiongradually increases in the direction away from the first electrode layer103 toward the piezoelectric layer 110.

Next, a method for manufacturing the ink jet head excluding the IC chipE of FIG. 5, i.e., the ink jet head including the pressure chambermember A, the actuator section B, the ink channel member C and thenozzle plate D illustrated in FIG. 6, will be described with referenceto FIG. 8A to FIG. 8C, FIG. 9A and FIG. 9B, FIG. 10A and FIG. 10B, FIG.11A and FIG. 11B, and FIG. 12A to FIG. 12D.

As illustrated in FIG. 8A, an adhesive layer 121, the first electrodelayer 103, the orientation control layer 104, the piezoelectric layer110, the second electrode layer 112, the vibration layer 111 and theintermediate layer 113 are deposited in this order on a substrate 120 bya sputtering method. Note that the adhesive layer 121 is similar to theadhesive layer 12 of Embodiment 1, and is formed between the substrate120 and the first electrode layer 103 in order to improve the adhesiontherebetween (it may not always be necessary to form the adhesive layer121). As will be described later, the adhesive layer 121 is subsequentlyremoved as is the substrate 120. Moreover, Cr is used as the material ofthe vibration layer 111, and Ti is used as the material of theintermediate layer 113.

A cut-out Si substrate having a size of 18 mm×18 mm is used as thesubstrate 120. The substrate 120 is not limited to an Si substrate, butmay alternatively be a glass substrate, a metal substrate, or a ceramicsubstrate. Moreover, the substrate size is not limited to 18 mm×18 mm,and a wafer having a diameter of 2 to 10 inches may be used as long asit is an Si substrate.

The adhesive layer 121 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate 120 to 400° C. in an argon gas at 1 Pa. The thickness of theadhesive layer 121 is 0.02 μm. Note that the material of the adhesivelayer 121 is not limited to Ti, but may alternatively be tantalum, iron,cobalt, nickel, chromium, or a compound thereof (including Ti).Moreover, the thickness is not limited to any particular thickness aslong as it is in the range of 0.005 to 0.2 μm.

The first electrode layer 103 is obtained by using a Pt alloy targetcontaining 3 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the substrate 120 to 500° C. in anargon gas at 1 Pa. The first electrode layer 103 has a thickness of 0.22μm, and is oriented along the (111) plane. Moreover, the Sr content is3.2 mol %. As is the first electrode layer 14 of Embodiment 1, the firstelectrode layer 103 may be made of at least one noble metal selectedfrom the group consisting of Pt, iridium, palladium and ruthenium towhich at least one additive selected from the group consisting of Mg,Ca, Sr, Ba, Al and oxides thereof is added (the amount of the additiveto be added is preferably greater than zero and less than or equal to 20mol %), and the thickness thereof is not limited to any particularthickness as long as it is in the range of 0.05 to 2 μm.

The orientation control layer 104 is obtained by using a sinter targetprepared by adding a 12 mol % excess of lead oxide (PbO) to PLTcontaining 13 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the substrate 120 to 600° C.in a mixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1)at a degree of vacuum of 0.8 Pa. The obtained lead lanthanum titanatefilm has a perovskite crystalline structure containing 10 mol % oflanthanum and containing lead 8% in excess of the stoichiometriccomposition, and is oriented along the (100) or (001) plane over Srlocated on one surface of the first electrode layer 103 that is closerto the orientation control layer 104 so that the cross-sectional area ofthe (100)- or (001)-oriented region gradually increases in the directionaway from the first electrode layer 103 toward the other side (i.e.,toward the piezoelectric layer 110). On the other hand, each region ofthe orientation control layer 104, which is located over a portion ofthe surface of the first electrode layer 103 where Sr does not exist, isnot oriented along the (100) or (001) plane, but such a region graduallyshrinks toward the piezoelectric layer 110. In the present embodiment,the thickness of the orientation control layer 104 is 0.03 μm, wherebythe (100)- or (001)-oriented region extends substantially across theentire surface of the orientation control layer 104 that is closer tothe piezoelectric layer 110.

Note that as with the orientation control layer 15 of Embodiment 1, theLa content of the orientation control layer 104 may be greater than zeroand less than or equal to 30 mol %, and the lead content thereof may bein excess of the stoichiometric composition by an amount greater thanzero and less than or equal to 30 mol %. Moreover, the material of theorientation control layer 104 may be PLZT obtained by adding zirconiumto PLT (the zirconium content is preferably 20 mol % or less), or may bea material obtained by adding at least one of magnesium and manganese toPLT or PLZT (the amount of magnesium and manganese to be added ispreferably greater than zero and less than or equal to 10 mol %).Furthermore, the orientation control layer 104 may be made of aperovskite oxide including strontium (particularly, strontium titanate).In such a case, the strontium titanate content may be equal to orgreater than 5 mol % and less than or equal to 100 mol %, i.e., onlystrontium titanate may be contained (in an amount of 100 mol %).Alternatively, lead titanate, PLZT, barium titanate, or the like, may becontained in addition to strontium titanate to form a solid solutionwith strontium titanate. Moreover, the thickness of the orientationcontrol layer 104 is not limited to any particular thickness as long asit is in the range of 0.01 to 0.2 μm. As described in Embodiment 1, theorientation control layer 104 may be omitted.

The piezoelectric layer 110 is obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 250 W thereto for 3hours while heating the substrate 120 to 570° C. in a mixed atmosphereof argon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuumof 0.3 Pa. The obtained PZT film has a rhombohedral perovskitecrystalline structure, and is oriented along the (100) plane. Moreover,the thickness of the piezoelectric layer 110 is 3 μm. Note that theZr/Ti composition of the piezoelectric layer 110 is not limited to anyparticular composition as long as it is in the range of 30/70 to 70/30,and the thickness thereof is not limited to any particular thickness aslong as it is in the range of 1 to 5 μm. Moreover, the material of thepiezoelectric layer 110 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used.

The second electrode layer 112 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa. The thickness of the secondelectrode layer 112 is 0.2 μm. Note that the material of the secondelectrode layer 112 is not limited to Pt as long as it is a conductivematerial, and the thickness thereof is not limited to any particularthickness as long as it is in the range of 0.1 to 0.4 μm.

The vibration layer 111 is obtained by using a Cr target and applying ahigh-frequency power of 200 W thereto for 6 hours at a room temperaturein an argon gas at 1 Pa. The thickness of the vibration layer 111 is 3μm. The material of the vibration layer 111 is not limited to Cr, butmay alternatively be nickel, aluminum, tantalum, tungsten, silicon, oran oxide or nitride thereof (e.g., silicon dioxide, aluminum oxide,zirconium oxide, silicon nitride), etc. Moreover, the thickness of thevibration layer 111 is not limited to any particular thickness as longas it is in the range of 2 to 5 μm.

The intermediate layer 113 is obtained by using a Ti target and applyinga high-frequency power of 200 W thereto for 5 hours at a roomtemperature in an argon gas at 1 Pa. The thickness of the intermediatelayer 113 is 5 μm. The material of the intermediate layer 113 is notlimited to Ti, but may alternatively be any suitable conductive metalmaterial such as Cr. Moreover, the thickness of the intermediate layer113 is not limited to any particular thickness as long as it is in therange of 3 to 10 μm.

On the other hand, the pressure chamber member A is formed asillustrated in FIG. 8B. The pressure chamber member A is formed by usinga substrate of a larger size than the Si substrate 120, e.g., a 4-inchwafer silicon substrate 130 (see FIG. 13). Specifically, a plurality ofpressure chamber cavities 101 are first formed by patterning in thesilicon substrate 130 (for forming the pressure chamber member). As canbe seen from FIG. 8B, in the patterning process, the width of apartition wall 102 b for partitioning pairs of four pressure chambercavities 101 from one another is set to be about twice as large as thatof the partition wall 102 a for partitioning the pressure chambercavities 101 from one another in each pair. Then, the patterned siliconsubstrate 130 is subjected to chemical etching, dry etching, or thelike, to form four pressure chamber cavities 101 for each pair, therebyobtaining the pressure chamber member A.

Thereafter, the silicon substrate 120 (for depositing films thereon)after the deposition process and the pressure chamber member A arebonded to each other with an adhesive. The application of the adhesiveis done by electrodeposition. Specifically, the adhesive 114 is firstapplied onto the bonding surface of the pressure chamber member A, i.e.,the upper surface of the pressure chamber partition walls 102 a and 102b, by electrodeposition, as illustrated in FIG. 8C. Specifically,although not shown, an Ni thin film having a thickness on the order of100 Å such that light can pass therethrough is formed as a baseelectrode film on the upper surface of the partition walls 102 a and 102b by a sputtering method, and then a patterned layer of the adhesiveresin agent 114 is formed on the Ni thin film. In this process, theelectrodeposition solution may be a solution obtained by adding 0 to 50%by weight of pure water to an acrylic resin aqueous dispersion, followedby thorough stirring and mixing. The Ni thin film is so thin that lightcan pass therethrough, so that it can easily be visually observed thatthe adhesive resin has completely attached to the silicon substrate 130(for forming the pressure chamber member). Experimentally, preferredelectrodeposition conditions include a solution temperature of about 25°C., a DC voltage of 30 V, and a voltage application time of 60 seconds,and an acrylic resin layer having a thickness of about 3 to 10 μm iselectrodeposited under these conditions on the Ni thin film of thesilicon substrate 130 (for forming the pressure chamber member).

Then, as illustrated in FIG. 9A, the Si substrate 120 (for depositingfilms thereon) after the deposition process and the pressure chambermember A are bonded to each other with the electrodeposited adhesive114. In the bonding process, the intermediate layer 113 deposited on thesubstrate 120 (for depositing films thereon) is used as thesubstrate-side bonding surface. Moreover, the Si substrate 120 (fordepositing films thereon) has a size of 18 mm, whereas the Si substrate130 for forming the pressure chamber member A is as large as 4 inches, aplurality (14 in the example illustrated in FIG. 13) of Si substrates120 (for depositing films thereon) are attached to a single pressurechamber member A (the Si substrate 130), as illustrated in FIG. 13. Theattachment is done while the center of each Si substrate 120 (fordepositing films thereon) is aligned with the center of the, widepartition wall 102 b of the pressure chamber member A, as illustrated inFIG. 9A. After the attachment, the pressure chamber member A is pressedagainst, and thus brought into close contact with, the Si substrate 120(for depositing films thereon) so that they are bonded to each otherfluid-tightly. Furthermore, the Si substrate 120 (for depositing filmsthereon) and the pressure chamber member A bonded to each other aregradually heated in a heating furnace so as to completely set theadhesive 114. Then, a plasma treatment is performed so as to removeexcessive portions of the adhesive 114.

Note that although the Si substrate 120 (for depositing films thereon)after the deposition process and the pressure chamber member A arebonded to each other in FIG. 9A, the Si substrate 130 (for forming thepressure chamber member) before the formation of the pressure chambercavities 101 may alternatively be bonded to the Si substrate 120 (fordepositing films thereon) after the deposition process.

Then, as illustrated in FIG. 9B, the intermediate layer 113 is etchedinto a predetermined pattern using the partition walls 102 a and 102 bof the pressure chamber member A as a mask (so that remaining portionsof the intermediate layer 113 are continuous with the partition walls102 a and 102 b (thus forming vertical walls)).

Then, as illustrated in FIG. 10A, the Si substrate 120 (for depositingfilms thereon) and the adhesive layer 121 are removed by etching.

Then, as illustrated in FIG. 10B, the first electrode layer 103 locatedabove the pressure chamber member A is etched by a photolithographytechnique so that the first electrode layer 103 is divided into portionseach corresponding to one pressure chamber 102.

Then, as illustrated in FIG. 11A, the orientation control layer 104 andthe piezoelectric layer 110 are etched by a photolithography techniqueso as to be divided into portions arranged in a pattern similar to thatof the first electrode layer 103. The remaining portions of the firstelectrode layer 103, the orientation control layer 104 and thepiezoelectric layer 110 after the etching process are located above therespective pressure chambers 102. The center of the width of each of thefirst electrode layer 103, the orientation control layer 104 and thepiezoelectric layer 110 precisely corresponds to the center of the widthof the corresponding pressure chamber 102. Thus, the first electrodelayer 103, the orientation control layer 104 and the piezoelectric layer110 are divided into portions each corresponding to one pressure chamber102, and then the silicon substrate 130 (for forming the pressurechamber member) is cut along the wide partition walls 102 b, therebyobtaining four sets of the pressure chamber member A, each includingfour pressure chambers 102, and the actuator section B fixed to theupper surface of the pressure chamber member A, as illustrated in FIG.11B.

Then, as illustrated in FIG. 12A, the common ink chamber 105, the supplyports 106 and the ink channels 107 are formed in the ink channel memberC, and the nozzle holes 108 are formed in the nozzle plate D. Then, asillustrated in FIG. 12B, the ink channel member C and the nozzle plate Dare bonded together with an adhesive 109.

Then, as illustrated in FIG. 12C, an adhesive (not shown) is transferredonto the lower surface of the pressure chamber member A or the uppersurface of the ink channel member C, and the pressure chamber member Aand the ink channel member C are bonded together after they are alignedwith each other. Through the process as described above, the ink jethead including the pressure chamber member A, the actuator section B,the ink channel member C and the nozzle plate D is completed, asillustrated in FIG. 12D.

The displacement in the thickness direction of a portion of thevibration layer 111 corresponding to the pressure chamber 102 wasmeasured while applying a predetermined voltage between the firstelectrode layer 103 and the second electrode layer 112 of an ink jetbead obtained as described above. The deviation in the displacement wasσ=1.8%. Moreover, after applying a 20 V AC voltage having a frequency of20 kHz for 10 days, deterioration in the ink-discharge performance wasnot observed with no ink-discharge defect.

Furthermore, similar results were obtained for an ink jet head where theadditive to the Pt film of the first electrode layer 103 was changed toAl (contained in an amount of 3.2 mol %).

On the other hand, an ink jet head similar to the ink jet head of thepresent invention was produced except that the orientation control layer104 was not provided and the additive to the Pt film of the firstelectrode layer 103 was changed (using Ti as the additive as inComparative Examples 1 to 3 of Embodiment 1). The displacement in thethickness direction of a portion of the vibration layer 111corresponding to the pressure chamber 102 was measured while applying apredetermined voltage between the first electrode layer 103 and thesecond electrode layer 112 of the ink jet head. The deviation in thedisplacement was σ=7.2%. Moreover, after applying a 20 V AC voltagehaving a frequency of 20 kHz for 10 days, an ink-discharge defect wasobserved in locations corresponding to about 30% of all the pressurechambers 102. This was not due to clogging of ink, etc. It is thereforebelieved that the actuator section B (the piezoelectric element) had apoor durability.

Thus, it can be seen that the ink jet head of the present embodiment hasa desirable durability with a small deviation in the ink-dischargeperformance.

Embodiment 3

FIG. 14 illustrates an important part of another ink jet head accordingto an embodiment of the present invention. In the ink jet head of thepresent embodiment, a substrate is used both for depositing filmsthereon and for forming the pressure chamber member, rather than usingseparate substrates, one for depositing films thereon and another forforming the pressure chamber member, as in the ink jet head ofEmbodiment 2.

Specifically, a vibration layer 403, an adhesive layer 404, a firstelectrode layer 406 (common electrode), an orientation control layer407, a piezoelectric layer 408 and a second electrode layer 409(separate electrode) are layered in this order on a pressure chambersubstrate 401 (pressure chamber member) in which pressure chambers 402have been formed by an etching process. The first electrode layer 406,the orientation control layer 407, the piezoelectric layer 408 and thesecond electrode layer 409 are arranged in this order to form apiezoelectric element. Moreover, the vibration layer 403 is provided onone surface of the piezoelectric element that is closer to the firstelectrode layer 406 via the adhesive layer 404. The adhesive layer 404is provided for improving the adhesion between the vibration layer 403and the first electrode layer 406, and may be omitted as the adhesivelayer 121 of Embodiment 2. The materials of the adhesive layer 404, thefirst electrode layer 406, the orientation control layer 407, thepiezoelectric layer 408 and the second electrode layer 409 are similarto those of the adhesive layer 121, the first electrode layer 103, theorientation control layer 104, the piezoelectric layer 110 and thesecond electrode layer 112, respectively, of Embodiment 2. Moreover, thestructures of the orientation control layer 407 and the piezoelectriclayer 408 are similar to those of the orientation control layer 104 andthe piezoelectric layer 110, respectively. In the vicinity of onesurface of the orientation control layer 407 that is closer to the firstelectrode layer 406, a (100)- or (001)-oriented region extends over Srlocated on one surface of the first electrode layer 406 that is closerto the orientation control layer 407 so that the cross-sectional area ofsuch a region in the direction perpendicular to the thickness directiongradually increases in the direction away from the first electrode layer406 toward the piezoelectric layer 408.

An Si substrate having a diameter of 4 inches and a thickness of 200 μmis used as the pressure chamber substrate 401. Also in this embodiment,the substrate 401 is not limited to an Si substrate, but mayalternatively be a glass substrate, a metal substrate, or a ceramicsubstrate.

In the present embodiment, the vibration layer 403 has a thickness of2.8 μm and is made of silicon dioxide. Note that the material of thevibration layer 403 is not limited to silicon dioxide, but mayalternatively be any of those mentioned in Embodiment 2 (nickel,chromium, etc., or an oxide or nitride thereof). Moreover, the thicknessof the vibration layer 111 is not limited to any particular thickness aslong as it is in the range of 0.5 to 10 μm.

Next, a method for manufacturing the ink jet head as described abovewill be described with reference to FIG. 15A and FIG. 15B.

First, as illustrated in FIG. 15A, the vibration layer 403, the adhesivelayer 404, the first electrode layer 406, the orientation control layer407, the piezoelectric layer 408 and the second electrode layer 409 areformed in this order by a sputtering method on the pressure chambersubstrate 401 on which the pressure chambers 402 have not been formed.

The vibration layer 403 is obtained by using a silicon dioxide sintertarget and applying a high-frequency power of 300 W thereto for 8 hoursat a room temperature without heating the pressure chamber substrate 401in a mixed atmosphere of argon and oxygen at 0.4 Pa (gas volume ratio:Ar:O₂=5:25). Note that deposition method for the vibration layer 403 isnot limited to a sputtering method, but may alternatively be a thermalCVD method, a plasma CVD method, a sol-gel method, or the like, or itmay alternatively be formed through a thermal oxidization process on thepressure chamber substrate 401.

The adhesive layer 404 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thepressure chamber substrate 401 to 400° C. in an argon gas at 1 Pa. Thethickness of the adhesive layer 404 is 0.03 μm. Note that the materialof the adhesive layer 404 is not limited to Ti, but may alternatively betantalum, iron, cobalt, nickel, chromium, or a compound thereof(including Ti). Moreover, the thickness is not limited to any particularthickness as long as it is in the range of 0.005 to 0.1 μm.

The first electrode layer 406 is obtained by using a Pt alloy targetcontaining 3 mol % of Sr and applying a high-frequency power of 200 Wthereto for 12 minutes while heating the pressure chamber substrate 401to 500° C. in an argon gas at 1 Pa. The first electrode layer 406 has athickness of 0.22 μm, and is oriented along the (111) plane. Moreover,the Sr content is 3.2 mol %. As is the first electrode layer 14 ofEmbodiment 1, the first electrode layer 406 may be made of at least onenoble metal selected from the group consisting of Pt, iridium, palladiumand ruthenium to which at least one additive selected from the groupconsisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added (the amountof the additive to be added is preferably greater than zero and lessthan or equal to 20 mol %), and the thickness thereof is not limited toany particular thickness as long as it is in the range of 0.05 to 2 μm.

The orientation control layer 407 is obtained by using a sinter targetprepared by adding a 12 mol % excess of lead oxide (PbO) to PLTcontaining 13 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the pressure chambersubstrate 401 to 600° C. in a mixed atmosphere of argon and oxygen (gasvolume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa. The obtainedlead lanthanum titanate film is the same as the orientation controllayer 104 of Embodiment 2.

Note that as with the orientation control layer 15 of Embodiment 1, theLa content of the orientation control layer 407 may be greater than zeroand less than or equal to 30 mol %, and the lead content thereof may bein excess of the stoichiometric composition by an amount greater thanzero and less than or equal to 30 mol %. Moreover, the material of theorientation control layer 407 may be PLZT obtained by adding zirconiumto PLT (the zirconium content is preferably 20 mol % or less), or may bea material obtained by adding at least one of magnesium and manganese toPLT or PLZT (the amount of magnesium and manganese to be added ispreferably greater than zero and less than or equal to 10 mol %).Furthermore, the orientation control layer 407 may be made of aperovskite oxide including strontium (particularly, strontium titanate).In such a case, the strontium titanate content may be equal to orgreater than 5 mol % and less than or equal to 100 mol %, i.e., onlystrontium titanate may be contained (in an amount of 100 mol %).Alternatively, lead titanate, PLZT, barium titanate, or the like, may becontained in addition to strontium titanate to form a solid solutionwith strontium titanate. Moreover, the thickness of the orientationcontrol layer 407 is not limited to any particular thickness as long asit is in the range of 0.01 to 0.2 μm. The orientation control layer 407may be omitted.

The piezoelectric layer 408 is obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 250 W thereto for 3hours while heating the pressure chamber substrate 401 to 570° C. in amixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1) at adegree of vacuum of 0.3 Pa. The obtained PZT film is the same as thepiezoelectric layer 110 of Embodiment 2. Note that the Zr/Ti compositionof the piezoelectric layer 408 is not limited to any particularcomposition as long as it is in the range of 30/70 to 70/30, and thethickness thereof is not limited to any particular thickness as long asit is in the range of 1 to 5 μm. Moreover, the material of thepiezoelectric layer 408 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used.

The second electrode layer 409 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa. The thickness of the secondelectrode layer 409 is 0.2 μm. Note that the material of the secondelectrode layer 409 is not limited to Pt as long as it is a conductivematerial, and the thickness thereof is not limited to any particularthickness as long as it is in the range of 0.1 to 0.4 μm.

Then, a resist is applied by a spin coating method on the secondelectrode layer 409, and then patterned through exposure and developmentprocesses into a pattern corresponding to the pressure chambers 402 tobe formed. Then, the second electrode layer 409, the piezoelectric layer408 and the orientation control layer 407 are divided into portions byetching. The etching process is a dry etching process using a mixed gasof argon and an organic gas including fluorine element.

Then, as illustrated in FIG. 15B, the pressure chambers 402 are formedin the pressure chamber substrate 401. The pressure chambers 402 areformed by an anisotropic dry etching process using a sulfur hexafluoridegas, an organic gas including fluorine element, or a mixed gas thereofSpecifically, the pressure chambers 402 are formed by performing ananisotropic dry etching after forming an etching mask on one surface ofthe pressure chamber substrate 401 that is opposite to the other surfacethereof on which various films have been formed so as to cover eachportion thereof corresponding to a side wall 413 to be formed.

Then, a nozzle plate 412 with nozzle holes 410 formed therein is bondedto the surface of the pressure chamber substrate 401 that is opposite tothe other surface thereof on which various films have been formed,thereby obtaining the ink jet head. The nozzle holes 410 are opened atpredetermined positions in the nozzle plate 412 by a photolithographymethod, a laser processing method, an electrical discharge machiningmethod, or the like. Then, before the nozzle plate 412 is bonded to thepressure chamber substrate 401, they are aligned with each other so thatthe nozzle holes 410 correspond to the pressure chambers 402,respectively.

The displacement in the thickness direction of a portion of thevibration layer 403 corresponding to the pressure chamber 402 wasmeasured while applying a predetermined voltage between the firstelectrode layer 406 and the second electrode layer 409 of an ink jethead obtained as described above. The deviation in the displacement wasσ=1.8%. Moreover, after applying a 20 V AC voltage having a frequency of20 kHz for 10 days, deterioration in the ink-discharge performance wasnot observed with no ink-discharge defect.

Furthermore, similar results were obtained for an ink jet head where theadditive to the Pt film of the first electrode layer 406 was changed toAl (contained in an amount of 3.2 mol %).

On the other hand, an ink jet head similar to the ink jet head of thepresent invention was produced except that the orientation control layer407 was not provided and the additive to the Pt film of the firstelectrode layer 406 was changed (using Ti as the additive as inComparative Examples 1 to 3 of Embodiment 1). The displacement in thethickness direction of a portion of the vibration layer 403corresponding to the pressure chamber 402 was measured while applying apredetermined voltage between the first electrode layer 406 and thesecond electrode layer 409 of the ink jet head. The deviation in thedisplacement was σ=5.8%. Moreover, after applying a 20 V AC voltagehaving a frequency of 20 kHz for 10 days, an ink-discharge defect wasobserved in locations corresponding to about 25% of all the pressurechambers 402. This was not due to clogging of ink, etc. It is thereforebelieved that the actuator section (the piezoelectric element) had apoor durability.

Thus, it can be seen that the ink jet head of the present embodiment hasa desirable durability and a small deviation in the ink-dischargeperformance, as the ink jet head of Embodiment 2.

Embodiment 4

FIG. 16 illustrates an ink jet recording apparatus 27 according to anembodiment of the present invention. The ink jet recording apparatus 27includes an ink jet head 28, which is similar to the ink jet head ofEmbodiment 2 or 3. The ink jet head 28 is configured so that ink in eachpressure chamber (the pressure chamber 102 of Embodiment 2 or thepressure chamber 402 of Embodiment 3) is discharged through a nozzlehole (the nozzle hole 108 of Embodiment 2 or the nozzle hole 410 ofEmbodiment 3), which is communicated to the pressure chamber, onto arecording medium 29 (e.g., recording paper) for recording information.

The ink jet head 28 is mounted on a carriage 31, which is provided on acarriage shaft 30 extending in the primary scanning direction X, and isreciprocated in the primary scanning direction X as the carriage 31reciprocates along the carriage shaft 30. Thus, the carriage 31 formsrelative movement means for relatively moving the ink jet head 28 andthe recording medium 29 with respect to each other in the primaryscanning direction X.

Moreover, the ink jet recording apparatus 27 includes a plurality ofrollers 32 for moving the recording medium 29 in the secondary scanningdirection Y, which is substantially perpendicular to the primaryscanning direction X (width direction) of the ink jet head 28. Thus, theplurality of rollers 32 together form relative movement means forrelatively moving the ink jet head 28 and the recording medium 29 withrespect to each other in the secondary scanning direction Y. Note thatin FIG. 16, arrow Z represents the vertical direction.

While the ink jet head 28 is moved by the carriage 31 from one side tothe other in the primary scanning direction X, ink is discharged throughthe nozzle holes of the ink jet head 28 onto the recording medium 29.After one scan of recording operation, the recording medium 29 is movedby the rollers 32 by a predetermined amount, and then the next scan ofrecording operation is performed.

Since the ink jet recording apparatus 27 includes the ink jet head 28similar to that of Embodiment 2 or 3, the ink jet recording apparatus 27provides a desirable printing performance and durability.

Embodiment 5

FIG. 17 and FIG. 18 illustrate an angular velocity sensor according toan embodiment of the present invention. The angular velocity sensor hasa shape of a tuning fork, and can suitably be used in a vehicle-mountednavigation system, or the like.

The angular velocity sensor includes a substrate 500 made of a siliconwafer having a thickness of 0.3 mm (the substrate 500 may alternativelybe a glass substrate, a metal substrate or a ceramic substrate). Thesubstrate 500 includes a fixed portion 500 a, and a pair of vibratingportions 500 b extending from the fixed portion 500 a in a predetermineddirection (the direction of the rotation axis with respect to which theangular velocity is: to be detected; the y direction in FIG. 17 in thepresent embodiment). The fixed portion 500 a and the pair of vibratingportions 500 b together form a shape of a tuning fork as viewed in thethickness direction of the substrate 500 (the z direction in FIG. 17),and the pair of vibrating portions 500 b, corresponding to the arms of atuning fork, extend in parallel to each other while being arranged nextto each other in the width direction of the vibrating portions 500 b.

A first electrode layer 503, an orientation control layer 504, apiezoelectric layer 505 and a second electrode layer 506 are layered inthis order on the vibrating portions 500 b of the substrate 500 and aportion of the fixed portion 500 a close to the vibrating portions 500b. Note that also in the angular velocity sensor, it is preferred thatan adhesive layer is provided between the substrate 500 and the firstelectrode layer 503, as in the piezoelectric element of Embodiment 1.

The materials and the thicknesses of the first electrode layer 503, theorientation control layer 504, the piezoelectric layer 505 and thesecond electrode layer 506 are similar to those of the first electrodelayer 14, the orientation control layer 15, the piezoelectric layer 16and the second electrode layer 17, respectively, of Embodiment 1.Moreover, the structures of the orientation control layer 504 and thepiezoelectric layer 505 are similar to those of the orientation controllayer 15 and the piezoelectric layer 16, respectively. In the vicinityof one surface of the orientation control layer 504 that is closer tothe first electrode layer 503, a (100)- or (001)-oriented region extendsover titanium located on one surface of the first electrode layer 503that is closer to the orientation control layer 504 so that thecross-sectional area of such a region in the direction perpendicular tothe thickness direction gradually increases in the direction away fromthe first electrode layer 503 toward the piezoelectric layer 505.

On each vibrating portion 500 b, the second electrode layer 506 ispatterned into three portions, i.e., two driving electrodes 507 forvibrating the vibrating portion 500 b in the width direction thereof(the x direction in FIG. 17), and a detection electrode 508 fordetecting a displacement (deflection) of the vibrating portion 500 b inthe thickness direction thereof (the z direction).

The two driving electrodes 507 extend along the lateral edges of thevibrating portion 500 b that are opposing each other with respect to thewidth direction thereof (the x direction) and entirely across thevibrating portion 500 b in the longitudinal direction thereof (the ydirection). One end of each driving electrode 507 that is closer to thefixed portion 500 a forms a connection terminal 507 a on the fixedportion 500 a. Note that only one driving electrode 507 mayalternatively be provided on one of the opposite edges of each vibratingportion 500 b.

On the other hand, the detection electrode 508 extends in the centralportion of the vibrating portion 500 b with respect to the widthdirection thereof and entirely across the vibrating portion 500 b in thelongitudinal direction thereof As does the driving electrode 507, oneend of the detection electrode 508 that is closer to the fixed portion500 a forms a connection terminal 508 a on the fixed portion 500 a. Notethat a plurality of detection electrodes 508 may alternatively beprovided on each vibrating portion 500 b.

Note that the first electrode layer 503 forms a connection terminal 503a, extending away from the vibrating portion 500 b, on the fixed portion500 a between the pair of vibrating portions 500 b.

Applied between the first electrode layer 503 and the two drivingelectrodes 507 on the vibrating portion 500 b is a voltage having afrequency that is resonant with the proper oscillation of the vibratingportion 500 b so that the vibrating portion 500 b vibrates in the widthdirection thereof Specifically, two voltages of opposite polarity areapplied to the two driving electrodes 507 while the ground voltage isapplied to the first electrode layer 503, whereby when one lateral edgeof the vibrating portion 500 b expands, the other lateral edgecontracts, and thus the vibrating portion 500 b deforms toward thesecond lateral edge. On the other hand, when the first lateral edge ofthe vibrating portion 500 b contracts, the second lateral edge expands,and thus the vibrating portion 500 b deforms toward the first lateraledge. By repeating this operation, the vibrating portion 500 b vibratesin the width direction thereof Note that by applying a voltage to onlyone of the two driving electrodes 507 on each vibrating portion 500 b,the vibrating portion 500 b can be vibrated in the width directionthereof The pair of vibrating portions 500 b are configured so that theydeform in opposite directions with respect to the width directionthereof and in symmetry with each other with respect to the center lineL, which extends in the longitudinal direction of the vibrating portion500 b between the pair of vibrating portions 500 b.

In the angular velocity sensor having such a configuration, if anangular velocity ω about the center line L is applied while the pair ofvibrating portions 500 b are being vibrated in the width directionthereof (the x direction) symmetrically with respect to the center lineL, the two vibrating portions 500 b are bent and deformed in thethickness direction (the z direction) by the Coriolis force (the pair ofvibrating portions 500 b are bent by the same amount but in oppositedirections), thereby also bending the piezoelectric layer 505, and thusgenerating a voltage according to the magnitude of the Coriolis forcebetween the first electrode layer 503 and the detection electrode 508.Then, the angular velocity ω can be calculated based on the magnitude ofthe voltage (the Coriolis force).

The Coriolis force Fc is expressed as follows:

-   -   Fc=2mvω, where v denotes the velocity of each vibrating portion        500 b in the width direction, and m denotes the mass of each        vibrating portion 500 b.

Thus, the value of the angular velocity ω can be obtained from theCoriolis force Fc.

Next, a method for manufacturing the angular velocity sensor will bedescribed with reference to FIG. 19A to FIG. 19F and FIG. 20.

As illustrated in FIG. 19A, the substrate 500 made of a 4-inch siliconwafer having a thickness of 0.3 mm is provided (see the plan view ofFIG. 20). Then, as illustrated in FIG. 19B, the first electrode layer503 is formed on the substrate 500 by a sputtering method under similarconditions to those of Embodiment 1.

Then, as illustrated in FIG. 19C, the orientation control layer 504 isformed on the first electrode layer 503 by a sputtering method undersimilar conditions to those of Embodiment 1. As described in Embodiment1 above, in the vicinity of one surface of the orientation control layer504 that is closer to the first electrode layer 503, a (100)- or(001)-oriented region extends over titanium so that the cross-sectionalarea of the region in the direction perpendicular to the thicknessdirection gradually increases in the upward direction away from thefirst electrode layer 503.

Then, as illustrated in FIG. 19D, the piezoelectric layer 505 is formedon the orientation control layer 504 by a sputtering method undersimilar conditions to those of Embodiment 1. As described in Embodiment1, the piezoelectric layer 505 is rhombohedral, with the degree of (001)orientation thereof being 90% or more.

Then, as illustrated in FIG. 19E, the second electrode layer 506 isformed on the piezoelectric layer 505 by a sputtering method undersimilar conditions to those of Embodiment 1.

Then, as illustrated in FIG. 19F and FIG. 20, the second electrode layer506 is patterned so as to form the driving electrodes 507 and thedetection electrode 508. Specifically, a photosensitive resin is appliedon the second electrode layer 506 and is exposed to light to form thepattern of the driving electrodes 507 and the detection electrode 508,and the unexposed portions of the photosensitive resin are removed. Thesecond electrode layer 506 is etched and removed in locations where thephotosensitive resin has been removed. Then, the photosensitive resin onthe driving electrodes 507 and the detection electrode 508 is removed.

After patterning the second electrode layer 506, the piezoelectric layer505, the orientation control layer 504 and the first electrode layer 503are patterned in similar steps, and the substrate 500 is patterned,thereby forming the fixed portion 500 a and the vibrating portions 500b. Thus, the angular velocity sensor is obtained.

Note that the deposition method for the various layers is not limited toa sputtering method, but may alternatively be any other suitabledeposition method as long as a crystalline thin film is directly formedwithout the crystallization step using a heat treatment (e.g., a CVDmethod).

Now, a conventional angular velocity sensor will be described withreference to FIG. 21 and FIG. 22.

The conventional angular velocity sensor includes a piezoelectric member600 made of quartz having a thickness of 0.3 mm. As does the substrate500 of the angular velocity sensor of the present embodiment, thepiezoelectric member 600 includes a fixed portion 600 a, and a pair ofvibrating portions 600 b extending from the fixed portion 600 a in onedirection (the y direction in FIG. 21) in parallel to each other. Thedriving electrodes 603 for vibrating the vibrating portion 600 b in thewidth direction thereof (the x direction in FIG. 21) are providedrespectively on two surfaces of the vibrating portion 600 b opposingeach other in the thickness direction thereof (the z direction in FIG.21), and detection electrodes 607 for detecting the displacement of thevibrating portion 600 b in the thickness direction are providedrespectively on two side surfaces of the vibrating portion 600 b.

In the conventional angular velocity sensor, a voltage having afrequency that is resonant with the proper oscillation of the vibratingportion 600 b is applied between the two driving electrodes 603 of eachvibrating portion 600 b so as to vibrate the pair of vibrating portions600 b in the width direction thereof (the x direction) symmetricallywith respect to the center line L between the pair of vibrating portions600 b, as in the angular velocity sensor of the present embodiment. Ifan angular velocity ω about the center line L is applied in this state,the pair of vibrating portions 600 b are bent and deformed in thethickness direction (the z direction) by the Coriolis force, therebygenerating a voltage according to the magnitude of the Coriolis forcebetween the two the detection electrodes 607 of each vibrating portion600 b. Then, the angular velocity ω can be calculated based on themagnitude of the voltage (the Coriolis force).

Since the conventional angular velocity sensor uses the piezoelectricmember 600 made of quartz, the piezoelectric constant is as low as −3pC/N. Moreover, since the fixed portion 600 a and the vibrating portion600 b are machined, it is difficult to reduce the size thereof, and thedimensional precision thereof is low.

In contrast, in the angular velocity sensor of the present embodiment,the portion for detecting the angular velocity (the vibrating portion500 b) is the piezoelectric element having a similar structure to thatof Embodiment 1. Therefore, the piezoelectric constant can be increasedto be about 40 times as large as that of the conventional angularvelocity sensor, and thus the size thereof can be reduced significantly.Moreover, minute processing with thin film formation techniques can beused, thereby significantly improving the dimensional precision.Furthermore, even if the angular velocity sensors are mass-producedindustrially, it is possible to obtain angular velocity sensors with ahigh characteristics reproducibility and a small characteristicsdeviation, and with a high breakdown voltage and a high reliability.

Note that also in the angular velocity sensor of the present embodiment,as in the piezoelectric element of Embodiment 1, the La content of theorientation control layer 504 may be greater than zero and less than orequal to 30 mol %, and the lead content thereof may be in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %. Moreover, the material of the orientation controllayer 504 may be PLZT obtained by adding zirconium to PLT (the zirconiumcontent is preferably 20 mol % or less), or may be a material obtainedby adding at least one of magnesium and manganese to PLT or PLZT (theamount of magnesium and manganese to be added is preferably greater thanzero and less than or equal to 10 mol %). Furthermore, the orientationcontrol layer 504 may be made of a perovskite oxide including strontium(particularly, strontium titanate). In such a case, the strontiumtitanate content may be equal to or greater than 5 mol % and less thanor equal to 100 mol %, i.e., only strontium titanate may be contained(in an amount of 100 mol %). Alternatively, lead titanate, PLZT, bariumtitanate, or the like, may be contained in addition to strontiumtitanate to form a solid solution with strontium titanate. Theorientation control layer 504 may be omitted.

Moreover, the first electrode layer 503 may be made of at least onenoble metal selected from the group consisting of platinum, iridium,palladium and ruthenium to which at least one additive selected from thegroup consisting of Mg, Ca, Sr, Ba, Al and oxides thereof is added (theamount of the additive to be added is preferably greater than zero andless than or equal to 20 mol %).

Furthermore, the material of the piezoelectric layer 505 is not limitedto any particular material, as long as it is a piezoelectric materialwhose main component is PZT, e.g., those obtained by adding an additivesuch as Sr, Nb or Al to PZT. For example, PMN or PZN may be used.

Furthermore, while only one pair of vibrating portions 500 b is providedin the substrate 500 in the angular velocity sensor of the presentembodiment, a plurality of pairs of vibrating portions may alternativelybe provided so as to detect angular velocities with respect to aplurality of axes extending in different directions.

Moreover, while the first electrode layer 503, the orientation controllayer 504, the piezoelectric layer 505 and the second electrode layer506 are layered in this order on the vibrating portions 500 b of thesubstrate 500 and a portion of the fixed portion 500 a close to thevibrating portions 500 b in the angular velocity sensor of the presentembodiment, these layers may alternatively be layered only on thevibrating portions 500 b.

In addition, while the piezoelectric element of the present invention isapplied to an ink jet head (an ink jet recording apparatus) and anangular velocity sensor in the embodiments described above, thepiezoelectric element of the present invention may be used in variousother applications including, but not limited to, thin film condensers,charge storage capacitors of non-volatile memory devices, various kindsof actuators, infrared sensors, ultrasonic sensors, pressure sensors,acceleration sensors, flow meters, shock sensors, piezoelectrictransformers, piezoelectric igniters, piezoelectric speakers,piezoelectric microphones, piezoelectric filters, piezoelectric pickups,tuning-fork oscillators, and delay lines. Particularly, thepiezoelectric element of the present invention may suitably be used in athin film piezoelectric actuator for a disk apparatus provided in a headsupporting mechanism, in which a head for recording or reproducinginformation to/from a disk being spun in a disk apparatus (a diskapparatus used as a storage device of a computer, etc.) is provided on asubstrate, wherein the substrate is deformed and the head is displacedby a thin film piezoelectric element provided on the substrate (see, forexample, Japanese Laid-Open Patent Publication No. 2001-332041). Thethin film piezoelectric element has a similar structure to thatdescribed in the embodiments above, in which the first electrode layer,the orientation control layer, the piezoelectric layer and the secondelectrode layer are layered in this order, with the second electrodelayer being bonded to the substrate.

1. A piezoelectric element, comprising: a first electrode layer; apiezoelectric layer provided on the first electrode layer; and a secondelectrode layer provided on the piezoelectric layer, wherein: the firstelectrode layer is made of a noble metal to which at least one additiveselected from the group consisting of Mg, Ca, Sr, Ba, Al and oxidesthereof is added; and the piezoelectric layer is made of a rhombohedralor tetragonal perovskite oxide that is preferentially oriented along a(001) plane. 2-6. (canceled)
 7. The piezoelectric element of claim 1,wherein the first electrode layer is made of at least one noble metalselected from the group consisting of platinum, iridium, palladium andruthenium.
 8. The piezoelectric element of claim 1, wherein an amount ofadditive to be added to the first electrode layer is greater than zeroand less than or equal to 20 mol %.
 9. The piezoelectric element ofclaim 1, wherein the piezoelectric layer is made of a piezoelectricmaterial whose main component is lead zirconate titanate.
 10. Thepiezoelectric element of claim 1, wherein: the first electrode layer isprovided on a substrate; and an adhesive layer for improving adhesionbetween the substrate and the first electrode layer is provided betweenthe substrate and the first electrode layer.
 11. An ink jet head,comprising: a piezoelectric element in which a first electrode layer, apiezoelectric layer and a second electrode layer are layered in thisorder; a vibration layer provided on one surface of the piezoelectricelement that is closer to the second electrode layer; and a pressurechamber member bonded to one surface of the vibration layer that is awayfrom the piezoelectric element and including a pressure chamber forstoring ink therein, in which the vibration layer is displaced in athickness direction by a piezoelectric effect of the piezoelectric layerof the piezoelectric element so as to discharge the ink out of thepressure chamber, wherein: the first electrode layer of thepiezoelectric element is made of a noble metal to which at least oneadditive selected from the group consisting of Mg, Ca, Sr, Ba, Al andoxides thereof is added; and the piezoelectric layer is made of arhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane.
 12. (canceled)
 13. An ink jet head,comprising: a piezoelectric element in which a first electrode layer, apiezoelectric layer and a second electrode layer are layered in thisorder; a vibration layer provided on one surface of the piezoelectricelement that is closer to the first electrode layer; and a pressurechamber member bonded to one surface of the vibration layer that is awayfrom the piezoelectric element and including a pressure chamber forstoring ink therein, in which the vibration layer is displaced in athickness direction by a piezoelectric effect of the piezoelectric layerof the piezoelectric element so as to discharge the ink out of thepressure chamber, wherein: the first electrode layer of thepiezoelectric element is made of a noble metal to which at least oneadditive selected from the group consisting of Mg, Ca, Sr, Ba, Al andoxides thereof is added; and the piezoelectric layer is made of arhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane.
 14. (canceled)
 15. An angular velocitysensor, comprising a substrate including a fixed portion and at least apair of vibrating portions extending from the fixed portion in apredetermined direction, in which a first electrode layer, apiezoelectric layer and a second electrode layer are layered in thisorder at least on each of the vibrating portions of the substrate, andthe second electrode layer on each of the vibrating portions ispatterned into at least one driving electrode for vibrating thevibrating portion in a width direction thereof and at least onedetection electrode for detecting a displacement of the vibratingportion in a thickness direction thereof, wherein: the first electrodelayer is made of a noble metal to which at least one additive selectedfrom the group consisting of Mg, Ca, Sr, Ba, Al and oxides thereof isadded; and the piezoelectric layer is made of a rhombohedral ortetragonal perovskite oxide that is preferentially oriented along a(001) plane. 16-24. (canceled)
 25. An ink jet recording apparatus,comprising an ink jet head, the ink jet head including: a piezoelectricelement in which a first electrode layer, a piezoelectric layer and asecond electrode layer are layered in this order; a vibration layerprovided on one surface of the piezoelectric element that is closer tothe second electrode layer; and a pressure chamber member bonded to onesurface of the vibration layer that is away from the piezoelectricelement and including a pressure chamber for storing ink therein, theink jet head being capable of being relatively moved with respect to arecording medium, in which while the ink jet head is moved with respectto the recording medium, the vibration layer is displaced in a thicknessdirection by a piezoelectric effect of the piezoelectric layer of thepiezoelectric element in the ink jet head so as to discharge the ink outof the pressure chamber through a nozzle hole communicated to thepressure chamber onto the recording medium, thereby recordinginformation, wherein: the first electrode layer of the piezoelectricelement in the ink jet head is made of a noble metal to which at leastone additive selected from the group consisting of Mg, Ca, Sr, Ba, Aland oxides thereof is added; and the piezoelectric layer is made of arhombohedral or tetragonal perovskite oxide that is preferentiallyoriented along a (001) plane.
 26. (canceled)
 27. An ink jet recordingapparatus, comprising an ink jet head, the ink jet head including: apiezoelectric element in which a first electrode layer, a piezoelectriclayer and a second electrode layer are layered in this order; avibration layer provided on one surface of the piezoelectric elementthat is closer to the first electrode layer; and a pressure chambermember bonded to one surface of the vibration layer that is away fromthe piezoelectric element and including a pressure chamber for storingink therein, the ink jet head being capable of being relatively movedwith respect to a recording medium, in which while the ink jet head ismoved with respect to the recording medium, the vibration layer isdisplaced in a thickness direction by a piezoelectric effect of thepiezoelectric layer of the piezoelectric element in the ink jet head soas to discharge the ink out of the pressure chamber through a nozzlehole communicated to the pressure chamber onto the recording medium,thereby recording information, wherein: the first electrode layer of thepiezoelectric element in the ink jet head is made of a noble metal towhich at least one additive selected from the group consisting of Mg,Ca, Sr, Ba, Al and oxides thereof is added; and the piezoelectric layeris made of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane.
 28. (canceled)
 29. Thepiezoelectric element of claim 1, wherein the additive exists on asurface of the first electrode layer that is closer to the piezoelectriclayer.
 30. The piezoelectric element of claim 1, wherein the additiveexists in a dotted pattern on a surface of the first electrode layerthat is closer to the piezoelectric layer.
 31. The piezoelectric elementof claim 1, wherein the first electrode layer is formed on thesubstrate.